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    By seabass, in Beginners Articles,

    A Look at Ammonia
    It's not uncommon for reef keepers to either fixate on, or ignore ammonia levels.  When in reality, it's just another parameter which provides information about the state of our reef tanks.  We'll look at the different types of ammonia, their toxicity levels, and how to interpret a positive test result.
    Types of Ammonia
    NH3 represents free ammonia, which is toxic in higher concentrations NH3-N represents the nitrogen content of NH3 without the hydrogen component NH4 represents ammonium, which within normal ranges, is harmless to marine life NH4-N represents the nitrogen content of ammonium, without hydrogen Total ammonia (a.k.a. TAN, or total ammonia nitrogen) is the sum of NH3 and NH4  
    The concentration of NH3 is greatly dependent on the potential of hydrogen (pH).  Chemical reactions will quickly convert free ammonia to ammonium, and vice versa based on pH.  The lower the pH, the less NH3 will be in the water.  The following graph shows the percentage of NH3 to NH4 at different pH levels:
    Figure 1: Percentage of Ammonia in Seawater[1]

    Note:  Here are a couple of calculators which (by entering your water's: salinity, pH, and temperature) can either compute total ammonia from NH3, or NH3 from total ammonia.
    Toxicity Levels of Ammonia
    Reef tank parameter tables often recommend keeping ammonia levels undetectable, or they might mention "typical" ocean values of less than 0.1 ppm.  Plus, we've probably all read that free ammonia (NH3) is toxic to marine life, which I feel has led to some confusion about ammonia levels in our reef tanks.  It's not the presence of NH3 which is a problem, but the concentration which determines toxicity.  Our livestock is typically much less affected by low (but still measurable) levels of ammonia than many of us realize.  So what level of NH3 is considered safe?
    Both the Seachem Ammonia Alert badge and the Seneye Reef monitor categorize NH3 toxicity levels as follows:[2]

    Safe: up to 0.02 ppm (or up to 0.25 ppm of total ammonia) Alert: up to 0.05 ppm (or up to 0.63 ppm of total ammonia) Alarm: up to 0.20 ppm (or up to 2.53 ppm of total ammonia) Toxic: up to 0.50 ppm (or up to 6.33 ppm of total ammonia) Note: The above total ammonia levels were rounded to the nearest hundredth, and computed assuming 1.026 sg, 8.2 pH, and 80° F.
    Scientific papers often refer to lethal concentrations which kill a specified percentage of organisms within a stated number of hours.  So "96 h LC50" describes a level of lethal concentration which kills 50% of the organisms within 96 hours.
    It's been reported that marine fish experience 96 h LC50 levels that range from 0.11 to 4.07 ppm of NH3 (or 1.39 to 51.50 ppm of total ammonia at: 1.026 sg, 8.2 pH, and 80° F).[3]  Note that this is a very broad range of ammonia levels, and that ammonia sensitivity varies by species of fish.  Plus, this is a very high rate of mortality within a short period of time; although even sub-lethal levels of ammonia can potentially cause problems.[1]
    Fish excrete a good portion of ammonia from their bodies through their gills, via diffusion (whereby the higher level of ammonia is diffused into the lower level of your tank's water).[1]  Acute toxicity can occur when high levels of ammonia in aquarium water prevent diffusion from occurring.  While this is simplified take on the subject, it helps to illustrate the point.
    Based on the NH3 toxicity categories above, (at a pH of 8.2 or less) I'd consider 0.25 ppm of total ammonia to be safe, with no corrective action required.  And while often well tolerated, we should typically look into the cause of total ammonia levels up to 0.5 ppm.  Our goal should really be to keep ammonia to a minimum.  Testing alerts us when something has changed, so we can decide if we just want to take note of it, or try to address it.
    Unfortunately, I haven't found anything which tells us what levels are considered safe for inverts.  So I could only guess if corals are equally affected by NH3 or not.  However, I speculate that they might be less affected.  But in any case, for the sake of our animals, I still feel that we should strive to keep NH3 to a minimum whenever possible.
    Ammonia Testing
    While ammonia is an important parameter, after the cycle is fully established, most reef keepers rarely test for it because spot checks almost always confirm that ammonia is within a safe range.  However, you might decide to check the level after observing visual signs of distress, experiencing a significant death in your tank, or following a particularly disruptive maintenance procedure or tank transfer.
    There are a number of ammonia test kits on the market (like API, Red Sea, Salifert, and others); all of which can be used to test for ammonia.  API is probably the most widely used ammonia test kit.  It's affordable, easy to use, and can effectively detect low levels of total ammonia before they become a danger to our livestock.  As someone who has used API's ammonia test kits for nearly two decades, I feel that it's gotten a bad rap for detecting safe levels of ammonia when there are no visible signs of livestock distress.  I actually feel that it's good when a test kit can detect these elevated, but safe, levels of total ammonia.
    Seachem uses a rather unique color changing disc to monitor NH3.  It comes in two options: the convenient Ammonia Alert badge (shown in the pic above) which continuously monitors NH3 in your tank for up to a year, and their MultiTest Ammonia kit which uses these same discs to report NH3 (but can also test for total ammonia).
    Finally, There are testers which use sensors to interpret the results (like Hanna and Seneye).  While they tend to be more expensive, a digital display might be helpful for people who have problems distinguishing colors, or shades of colors.
    Notes:  The use of Seachem Prime can affect the color of Nessler and salicylate based kits (respectively, either changing the color of the result, or showing an inflated level of ammonia).[4]  In addition, people have questioned the claims that dechlorinators such as Seachem Prime can actually detoxify ammonia; apparently, these products have little to no effect on NH3 (or the ratio of NH3 to NH4).
    Sources of Ammonia
    Dead organic matter, which is broken down by heterotrophic bacteria, will result in the production of ammonia.  So a substantial death or deaths can cause elevated ammonia levels.  Likewise, uneaten food which is broken down by bacteria is a source of ammonia.  And when fish consume food (a nitrogen source), they excrete the excess nitrogen through their gills in the form of ammonia.[1]  While we don't want to underfeed our animals, we should realize that overfeeding not only increases the ammonia production in your tank, but it adds to the organic material and inorganic nutrients in the water.
    A lesser known source of ammonia is from our salt mixes.  Ammonia is a common contaminate in magnesium chloride and calcium chloride.  This contamination can vary by the brand (and batch) of salt.  I've seen freshly mixed saltwater test as high as 0.25 ppm of total ammonia.  While this might sound like a lot, your tank's biofilter should typically be able to process the ammonia fairly quickly.
    https://www.reefkeeping.com/issues/2007-02/rhf/index.php https://answers.seneye.com/en/water_chemistry/what_is_ammonia_NH3_NH4/what_ammonia_level_is_safe Ammonia in estuaries and effects on fish. Eddy, F.B. Environmental and Applied Biology, University of Dundee, Dundee, UK. Journal of Fish Biology (2005), 67(6), 1495-1513. https://www.seachem.com/prime.php  
    Also check out:  A Guide to Cycling.
    A Guide to Reef Aquarium Cycling
    This topic is almost as old as reef keeping itself.  But within the past decade, governments have placed restrictions on live rock collection, and there's been a shift to starting new reef tanks with dry rock.  In this guide, I'll discuss the nitrogen cycle, as well as methods to cycle both live and dry rock (something which every new hobbyist should be aware of).
    I'll be using the following definitions:
    Bio-load noun - The wastes produced by the biological organisms in your tank
    Biofilter noun - The nitrifying bacteria which make up the nitrogen cycle
    Curing verb - The process of removing dead organics (an ammonia source) from your rock
    Cycle noun - The nitrogen cycle
    Cycle verb - To establish the nitrogen cycle
    And even if commonly used, I'll try to avoid using confusing terms like "cycle" to describe an ammonia spike.
    The Nitrogen Cycle
    The nitrogen cycle doesn't change, so I won't spend a lot of time on this well documented topic.  When it comes to the cycle, we are primarily concerned about nitrifying bacteria and ammonia.  However, nitrite and nitrate are also part of the nitrification process:
    Ammonia is produced by animals, including the breakdown of dead organic matter by heterotrophic bacteria. Nitrifying bacteria oxidizes the ammonia into nitrite (which isn't considered toxic in marine aquariums). Then nitrite is oxidized into nitrate (a critical nutrient for all photosynthetic life). Finally, excess nitrate can be exported via water changes. Nitrate can also be taken up by phytoplankton, macroalgae, seagrass, and animals with zooxanthellae (a symbiotic algae living within corals and other "photosynthetic" animals).  More advanced methods of nitrate reduction include: supporting consumption by dosing liquid carbon, and by providing anaerobic zones for denitrifying bacteria.
    Notes:  Nitrifying bacteria reside on the hard surfaces in your tank (like rocks, sand, equipment, and tank walls).  Therefore, water changes will not remove this critical bacteria.  In addition, you can transfer the biofilter from one tank to another tank by moving the rocks, filter media, etc.
    Cycling Live Rock
    Rock that has been taken from the ocean, or from another reef tank, is called live rock.  When you purchase it, the nitrifying bacteria get transferred along with the rock.  Plus, it usually contains more than just bacteria (including things like pods, worms, and coralline algae).  This biodiversity can often help prevent pests like dinoflagellates from taking over without biological competition.  For this type of rock, we should generally wait until total ammonia drops to a safe range (of 0.25 ppm or less) before adding livestock.
    Note:  Fully cured live rock will produce less ammonia than it can process, so it won't elevate ammonia levels.
    Uncured Live Rock
    Since collection restrictions have made it harder to acquire uncured live rock from the ocean, you might find aquacultured and maricultured rock to be acceptable alternatives.  To keep costs down, live rock is often shipped to you (or your local store) wet, but not submerged in water.  This usually results in some die off, which will produce ammonia.
    As the name suggests, uncured live rock has not gone through the curing process (where heterotrophic bacteria breaks down the dead organic compounds).  But generally, there's already enough nitrifying bacteria on these rocks, so it's just a matter of waiting until the dead organics are broken down and ammonia reaches safe levels (which could take a few weeks).  During this time, there are usually temporary spikes in both ammonia and nitrite. The following graph represents a typical cycle when using uncured live rock:
    Figure 2: Nitrogen Cycle With Ammonia Spike[1]

    Note:  Ammonia levels might remain slightly elevated following an ammonia spike. In addition (like in the ocean), tanks with livestock will always have some level of total ammonia, even if it's not detectable by our test kits.
    Cured Live Rock
    This rock has already been cured; so it has little to no die off, and is capable of processing more ammonia than it produces.  On the other hand, rock which hasn't been fully cured, or has experienced die off during transport, can produce elevated ammonia levels.  If it does, simply wait until total ammonia reaches a safe range (of 0.25 ppm or less) before slowly adding livestock.
    Cycling Dry Rock
    Dry rock is a term used for any reef rock which is currently dry.  It doesn't contain any marine life (including nitrifying bacteria to process ammonia).  This rock could have been manufactured or mined from the ground, or have come from someone else's tank or collected from the ocean (and then dried out).  Because of this, it might or might not have dead organic matter on it.
    If you have any question about whether or not your rock might contain dead organics, I recommend testing it, and curing it if necessary.  You can test it by soaking it in some water for a few days.  If the water becomes discolored or starts to smell, the organics are probably starting to break down (and ammonia is being produced).  You can test the water for ammonia to be certain.
    Curing Dry Rock
    If it turns out that your rock has dead organic matter on it, you should cure it like you would cycle uncured live rock.  When you are done, and depending on how much ammonia was produced, it should have a working biofilter capable of handling a light bio-load.
    Adding Nitrifying Bacteria
    You can use a bottled bacteria culture (such as Instant Ocean BIO-Spira) to introduce or add nitrifying bacteria strains to your dry rock.  The bacteria is immediately capable of processing ammonia, even when it's still free floating in the water column.  And within 5 days, the bacteria should colonize onto the hard surfaces in your tank; after this, water changes will no longer remove the newly added bacteria.  Uncured rock will produce ammonia; if it does, simply wait until the level of total ammonia reaches 0.25 ppm.
    If you stop there and slowly add livestock, your fish will usually be fine; although the ammonia levels could still become elevated until the the bacteria populations increase.  This is sometimes referred to as cycling with fish (where the ammonia from fish is used to help build up the biofilter).  However, if the ammonia level gets too high, it can be harmful to your fish.  So prior to adding livestock, I typically suggest using the following fishless cycling method to build up the nitrifying bacteria on dry rock; although you might not always have time for this step when setting up something like an emergency quarantine tank.
    Fishless Cycling
    The idea behind fishless cycling is to use a clean source of ammonia to build up the biofilter on pre-cured dry rock prior to stocking your tank.  This can be done in your display tank, or in a separate container with a powerhead for flow (a heater or light isn't required).
    While fishless cycling can be done without adding bottled bacteria, dosing nitrifying bacteria beforehand is usually recommended to speed up the process.[2]  The ammonia source used, will feed the bacteria and promote its reproduction.
    Fishless cycling is a simple process of: dosing, waiting, and testing.  The number of days that it takes isn't important; simply wait until your rocks are ready for the next step before proceeding:
    Dose ammonium chloride or another clean source of ammonia, so that total ammonia is between 1 and 2 ppm (don't overdose).  If you accidentally dose too much, you can perform a water change to bring down the level of ammonia. Wait for total ammonia to drop to 0.25 ppm  (if the level of total ammonia goes up, your rocks weren't fully cured, which will add time to this step). Repeat until your rocks can process the dosed ammonia down to 0.25 ppm within 24 hours. When finished, your tank will have a working biofilter capable of handling a typical initial bio-load.
    Notes: Don't add ammonia or ammonium to rock containing non-bacterial life (like pods or other inverts).  If using a pure ammonia cleaner as your ammonia source, make sure that it doesn't contain scents, surfactants, detergents, or dyes.
    Ghost Feeding
    Ghost feeding is an alternative method for adding an ammonia source to build up a biofilter.  It involves adding fish food to a tank (without any fish in it) until the biofilter can process the ammonia being produced.  And while effective, it's harder to control the level of ammonia, and the rotting food adds organics and phosphate, which could lead to future problems like cyanobacteria.
    Cycling a Combination of Dry and Live Rock
    We can add live rock to dry rock in order to introduce biodiversity.  The longer that you keep the dry rock and live rock together, the more life (like pods, bacteria, and coralline) will spread to the dry rock.  However, if the dry rock is uncured, you might choose to cure it separately, so as not to expose this beneficial life to the ammonia that is produced.
    Post Cycling
    After cycling your rocks (but before adding livestock), you can adjust the water's nutrient levels by: performing water changes to export excess nutrients, or by dosing nutrients if they are too low.  If you won't be keeping corals, I'd change out enough water to reduce nitrate to less than 20 ppm.
    If you will be keeping coral and anemones, I recommend trying to maintain nitrate levels between 3 and 10 ppm (dosing up to 3 ppm, or exporting down to 10 ppm).  Likewise, I recommend trying to keep phosphate levels between 0.03 to 0.10 ppm (dosing up to 0.03 ppm, or exporting down to 0.10 ppm).
    Once the cycle is established, and after you've adjusted the tank water's nutrient levels, I recommend adding livestock in smaller groups (waiting at least a week between additions).  This will give the bacteria populations some time to adjust to the new bio-load before adding more livestock.
    https://www.bulkreefsupply.com/content/post/md-2019-01-how-to-cycle-a-saltwater-tank-tips-to-help-you-succeed-with-your-new-aquarium https://www.drtimsaquatics.com/resources/library/quick-guide-to-fishless-cycling-with-one-and-only/  
    Also check out:  A Look at Ammonia.
    What and When to Test
    Which parameters and how frequently we test them often depends on how far along we are, and what we'll be keeping.  We should always be aware of the inorganic nutrient levels in our tanks; but certain tests can wait until we add corals, and others might not be necessary at all.  In this guide, I'll discuss the most commonly tested reef tank parameters, making some recommendations about when to test and how we might control their values.
    In addition, how often we test certain parameters typically changes over time.  Once you can accurately predict the values (prior to testing), you can usually check that parameter less often.  But since reef tanks are constantly changing; it's still necessary to periodically monitor the most critical parameters, even when you think they haven't changed.
    There are a variety of good kits and testing instruments available; and we often use different brands of test kits to check different parameters.  For example, I use a temperature controller to monitor and control temperature, an API test kit to check ammonia, and Salifert to test: alkalinity, calcium, and magnesium.  Over time, we usually develop our own personal preferences.
    Like most parameters, temperature stability is very important.  I usually recommended checking it when feeding your fish.  We use heaters, chillers, and fans to control temperature, and thermometers to verify its value.  A temperature controller can control the power to a heater, chiller, or fan when the temperature reaches a set value; plus they often have a digital thermometer and warning alarm.
    In nature, corals are typically found in warmer waters (up to 86° F).  Higher temperatures can increase the metabolism and growth rates of corals.  However, since oxygen is more soluble at lower temperatures, we usually try to keep our tanks a little cooler (like between 78 and 80° F).  Although, when temperatures are kept sable, it's generally considered safe to keep our reef tanks as warm as 84° F.
    We use refractometers, hydrometers, and conductivity meters to measure salinity.  For accuracy, I use RO/DI or distilled water to calibrate my refractometer to 1.000 sg.  But I'll confess, I mostly use a swing arm hydrometer (which I checked against my calibrated refractometer).
    Before each water change, I recommend checking the tank water's salinity, as well as the newly mixed saltwater (adjusting it as needed).  And to maintain stability and help ensure that specific gravity (sg) doesn't exceed 1.027, we regularly replace the evaporated water with freshwater (typically RO/DI, or distilled).  An automatic top off (ATO) unit can help automate this job.
    Salt creep and other factors can also affect salinity, so occasionally spot check your tank's water, and correct it if necessary.  While stability is important, most of our livestock is more tolerant to sudden decreases in salinity, than to sudden increases.  To raise salinity, I usually recommend topping off the evaporated water with saltwater until the desired salinity is achieved.
    We can use a test kit or a calibrated meter to monitor pH.  But since we don't usually try to change its value, I rarely bother testing it.  We're usually more concerned about keeping alkalinity stable than with achieving a particular pH.  I usually only recommend checking pH when you are actively changing its value (like when dosing Kalkwasser, or using a calcium reactor).
    However, excess CO2 lowers the water's pH.  Therefore, low pH can indicate too many fish, poor aeration, or the tank being in a room with high concentrations of CO2.  But assuming that the CO2 levels in the room are normal, a foam fractionator (protein skimmer) can increase gas exchange and help keep pH stable.  Likewise, an attached macroalgae refugium, that's lit when your tank lights are off, can also help stabilize your tank's pH.
    Notes:  If dosing, you might choose to add alkalinity at night (when pH is naturally lower).  Also, knowing your tank's pH level (in addition to the temperature and salinity) allows us to compute free ammonia from total ammonia, and vice versa.
    Ammonia is a nutrient which can be utilized by algae (and reportedly, even corals) in our tanks.  However, free ammonia (NH3) is toxic in higher concentrations, so we typically try to limit its presence.  We're primarily concerned about the build up of toxic ammonia when setting up a new tank (including quarantine and hospital tanks).
    But after the nitrogen cycle has become fully established, ammonia usually stays within a safe range, so there's typically little need to test for it.  Still, there are events which can increase ammonia production.  So we might test for ammonia if you see signs of distress or after a significant death, or even following a particularly disruptive event (such as a tank transfer, or disturbing a mature sand bed).
    We usually measure total ammonia or free ammonia.  The Seachem Ammonia Alert badge (shown above/right), continuously monitors free ammonia (NH3) for up to a year.  Whereas a total ammonia test kit shows us the sum of free ammonia and ammonium (NH3 and NH4).  The ratio between NH3 and NH4 is highly dependent on pH (with more free ammonia occurring at higher pH levels).
    Notes:  Here's a Total Ammonia Calculator (which can compute total ammonia from NH3), and a Free Ammonia Calculator (which can compute NH3 from total ammonia).  See A Look at Ammonia for more information about ammonia in our tanks.
    As part of the nitrogen cycle, ammonia is oxidized into nitrite.  But since nitrite isn't very toxic in a marine aquarium, testing this parameter usually has limited value.  Although, when your tank is in the process of establishing its nitrogen cycle, it can provide additional information about its progress.  I'll propose that testing nitrite is mostly beneficial when tracking the stages of a fishless cycle (the dosing of ammonia or ammonium chloride to build up the biofilter on dry rock).  But even then, this test isn't absolutely necessary.
    Note:  See A Guide to Reef Aquarium Cycling for more information about the nitrogen cycle.
    Nitrifying bacteria oxidizes nitrite into nitrate; which is an important source of nitrogen for photosynthetic life.  When keeping corals, you should always be aware of this nutrient's value, and try to keep it within the recommended range.  I suggest testing for nitrate once a week, or at least until you can accurately predict its value beforehand.  While certain inverts are more sensitive to high nitrate levels, fish are usually more tolerant; but try not to let it exceed 20 ppm.
    Food is the primary source of phosphate in our reef tanks; but overfeeding can also add excess organics, which could result in problems.  When keeping corals, adequate phosphate levels are arguably more critical than nitrate, and you should always be aware of its value.  And like nitrate, you should attempt to keep phosphate within the recommended range.
    Precisely determining phosphate levels (down to the hundreds of a part per million) can be challenging for any test kit.  But the digital readout from a Hanna Checker makes it easy to read the results.  Although, you can usually distinguish if phosphate is within the recommended range by using a traditional test kit (like from Salifert).
    Low nutrient levels will end up starving photosynthetic life; so when keeping corals, higher phosphate levels are generally preferred over lower levels.  And while higher levels can accelerate the growth rate of algae, it typically poses little other threat to our livestock.  That said, phosphate levels shouldn't exceed 0.2 ppm.
    Note:  API's phosphate test kit is a high range test (which is better suited for a freshwater planted tank), and can't detect the lower levels that are within the recommended range for reef tanks.
    If you are just keeping soft corals, you might not ever have to test alkalinity, as water changes (and dissolved rock and sand) will replenish most of the consumed elements.  However, stony corals (LPS and SPS) and calcified algae (such as coralline) need alkalinity, calcium, and magnesium to form their calcified structures (making testing necessary).
    At first, when the mass of stony coral is small, monthly testing of alkalinity might be adequate.  And since alkalinity levels change more dramatically than either calcium or magnesium (and because its stability is more critical), you only have to test alkalinity to determine when you need to start dosing elements.  But once you start dosing, you'll need to regularly test alkalinity, calcium, and magnesium (dosing them when necessary).
    Note:  It has been reported that when nutrient levels are too low, higher alkalinity levels can burn the tips of SPS corals.
    Coral skeletons are made up of calcium carbonate, so calcium levels are important.  Once you start dosing alkalinity, you'll need to test for and dose calcium as well.  Like any parameter, it's best to keep this level stable.  And while some salt brands mix calcium to over 500 ppm (which poses no risk to your livestock), I wouldn't feel the need to dose calcium back to more than 500 ppm.
    Magnesium is consumed along with alkalinity and calcium.  So after you start dosing alkalinity, you'll need to test for and dose magnesium as well.  Also, like calcium, higher levels are usually well tolerated; but there typically isn't a need to dose magnesium past 1400 ppm.
    Keeping the magnesium level within the recommended range allows our tanks to achieve the required alkalinity and calcium levels.  Think of magnesium as a bucket which holds alkalinity and calcium; if the bucket is too small, it won''t be able hold enough of these other two elements.
    Recommended  Reef Tank Levels
    Parameter: Recommended Range: Temperature 76 to 83° F Salinity 1.025 to 1.027 sg pH 7.8 to 8.3 Free Ammonia (NH3) Less than 0.02 ppm Total Ammonia
    (NH3 + NH4) Undetectable to 0.25 ppm
    (at 8.2 pH or less) Nitrate (NO3) 3 to 10 ppm Phosphate (PO4) 0.03 to 0.10 ppm Alkalinity* 7 to 12 dKH Calcium* 380 to 500 ppm Magnesium* 1250 to 1400 ppm *Ocean Values: Alk 7 dKH, Cal 420 ppm, Mag 1280 ppm  
    Note:  The above chart lists recommended ranges for coral reef tanks; certain values outside of these ranges might still be considered safe.
    Dosing and Nutrient Export
    Feeding adds inorganic nutrients to the water, which (along with other elements) are consumed by the photosynthetic life as it grows.  Partial water changes replenish a portion of the consumed elements and export some of the nutrients.  But in order to provide a healthy reef environment, we might need to adjust these parameters further (by exporting more of the excess nutrients, and by dosing insufficient nutrients and/or elements).
    For nutrients, I recommend dosing them up to the minimum level of its recommended range, and exporting excess nutrients down to the maximum level of its recommended range.  Additional ways to reduce excess nutrients include: binding agents, growing macroalgae, dosing carbon (like vinegar or vodka), or creating anaerobic zones to support denitrifying bacteria; but I won't be discussing these more advanced ways to export nutrients here.
    As the mass of stony corals and coralline increases, partial water changes will no longer be able to replenish all of the consumed elements.  These elements (as well as low nutrient levels) can be replenished by dosing them back into the water.  For elements, I recommend trying to match the levels of a newly mixed batch of saltwater.  This way, a large water change doesn't cause big parameter swings.  If the levels of your salt mix aren't to your needs or liking, I'd consider switching brands.
    For most reef tanks, I usually suggest sticking to dosing phosphate, nitrate, alkalinity, calcium, and magnesium (the parameters that we most commonly test for).  People sometimes get into trouble when dosing other things.  And only dose to replenish the elements which have been consumed (as reported by a test kit).  You can start dosing alkalinity, calcium, and magnesium after alkalinity drops 1 dKH below its original value.
    Notes:  Dosing alkalinity and calcium together will cause a snowstorm of precipitation; so wait at least a half an hour before dosing the second element.  Try to keep alkalinity swings to less than 1 dKH per day; dose multiple times a day if necessary (this can be automated with a dosing pump).  Also, avoid increasing calcium by more than 50 ppm per day, or increasing magnesium by more than 100 ppm per day.
    Through lots of experience and careful observation, it might be possible to delay (or even skip) certain tests.  However, until we become experienced reef keepers, testing will always provide us with the best look into the inner workings of our reef tanks, and help us maintain stable water parameters (which is an essential part of reef keeping).
    Marine Depot
    Many reef-keepers are under the impression that if they get water quality parameters to match a certain formula, their corals will color up and thrive. These parameters have aquarists chasing “numbers” and often lead them to making changes and constant adjustments to the aquarium at the expense of environmental stability. It’s possible to be so focused on chasing those specific numbers to achieve color and growth that you miss the bigger picture: achieving a stable environment. So, stop chasing “numbers” and keep the following discussed pillars (in this four part series) of reef-keeping stable to see what color and growth your coral can produce.
    You’ve seen beautiful, colorful reef tanks that have been running trouble-free for years. Ever wonder what the secret is? They’re not chasing numbers! They all were maintained by focusing on what we call the Four Pillars of Reef-keeping: Lighting, Water Flow, Nutrition and Filtration. Your focus should be on keeping these foundational factors stable… unchanging and stop focusing on chasing numbers. It’s a time-proven path to having great-looking corals and a beautiful reef tank. So, let’s jump into the First Pillar: Lighting.
    Read more.....
    A Quick Guide to Keeping Photosynthetic Gorgonians in Home Aquaria
    Hello fellow reefers! My name is Billy and I am a big fan of the beautiful, tree-like soft corals known as gorgonians. Despite their reputation as delicate animals that are difficult to keep in captivity, most photosynthetic gorgonians are extremely hardy, and some even make excellent starter corals for those just getting into the hobby. With this in mind I decided to create this quick and dirty guide to encourage more home aquarists to experiment with keeping these wonderful animals, as I consider them to be some of the most captivating and attractive corals in the sea.

    Eunicea flexuosa, a beautiful photosynthetic gorgonian.
    1. What is a Gorgonian?
    Gorgonians are colonial soft corals that belong to the order Alcyonacea. They are closely related to other softies such as leather corals (Sarcophyton, Sinularia, Capnella, etc.). They generally exhibit upright, branching growth patterns that make them look a lot like underwater bushes or trees, and attach themselves to hard surfaces with a matlike holdfast. Though some gorgonians incorporate calcified spicules into their tissues, most do not lay down a hard skeleton of calcium carbonate like reef-building corals do. Instead, their skeleton is made from a strong, flexible protein called gorgonin, around which the fleshy structure of the animal grows. Gorgonin is similar to the material found in human tendons, but has about twice as much tensile strength. This supple skeleton allows gorgonians to bend and sway in the current, evenly exposing the polyps on both sides of the colony to light and nutrients. Gorgonians and other Alcyonaceans are sometimes referred to as octocorals because their polyps have eight-fold symmetry (e.g. the number of tentacles on each polyp is always a multiple of eight). All gorgonians catch and eat plankton, and some also have symbiotic dinoflagellates called zooxanthellae that live inside of their tissues and make energy for them using sunlight. This article will focus on these photosynthetic species, as they are generally hardier and easier to keep in captivity than their azooxanthellate relatives.
    Photosynthetic gorgonians inhabit shallow tropical seas around the world, but a large majority of them come from the tropical Western Atlantic - namely the waters around Florida, the Bahamas, the Gulf of Mexico, and the Caribbean Sea. In the Indo-Pacific the same shallow, brightly-lit, wave-washed environments that Atlantic gorgonians call home are instead inhabited by various leather corals, which are not found in the Caribbean at all. The opposite is also true, with gorgonians being quite uncommon (though not entirely absent) in the Indo-Pacific regions where leather corals rule. The vast majority of the various species of photosynthetic gorognians available to hobbyists come from the waters around Florida and the Caribbean Sea.
    2. Care Requirements
    I. Flow
    Most photosynthetic gorgonians are hardy and fairly easy to keep, but they do have a few specific care requirements to keep in mind. First and foremost is flow. Almost all gorgonians like fairly robust water movement, but too much flow can interfere with their feeding. Flow should be strong enough to stir the colony's branches but not so strong that the animal is blowing over or knocking into its neighbors. If you notice that your gorgonian's polyps are struggling to open or are periodically shutting and then opening again as the colony is buffeted by the current, then you may want to dial down your flow a bit. Indirect, semi-randomized flow is generally best; most of the time it is better to bounce flow off the glass or rockwork rather than pointing a powerhead directly at your gorgonians.
    Also, most gorgonians prefer to be oriented perpendicular to the current, with the flow passing over and through the mass of their branches. In nature these animals often inhabit shallow hardbottom areas that are swept by strong, uni-directional laminar currents which reverse periodically with the changing of the tides. A setup involving two wavemakers at opposite ends of a long tank that provide alternating flow throughout the day would be ideal for most gorgonians, but in smaller systems where this is not an option a single powerhead is generally more than sufficient as long as it is positioned properly. Many of the more fan-shaped species also enjoy wavelike flow patterns that cause their branches to flap back and forth from side to side. This motion ensures that the polyps on both sides of the animal are alternately shaded and exposed to light, maximizing the colony's potential for photosynthesis.
    II. Light
    Photosynthetic gorgonians of course require sufficient light to grow, and most of them can handle quite a bit of it. Many genera commonly found in the aquarium trade (e.g. Pterogorgia, Eunicea, Muriceopsis) come from very shallow water and are regularly exposed to intense sunlight. Some can tolerate a bit less light though, and pretty much all gorgonians are considered less picky about light than SPS or even LPS corals. Generally speaking any light strong enough to keep LPS corals like Blastomussa etc. is probably good enough for gorgonians as well. I keep mine under a 15 watt Kessil A80 LED, and even this fairly weak light has given me good results so far.
    Like most zooxanthellate corals, gorgonians will take some time to adjust to your aquarium's lighting regimen after being added to your tank. Under bright lights newly introduced colonies will sometimes expand the polyps near their base first, with extension working up the colony's stalk as it becomes accustomed to the light. Some species are a bit more picky than others of course, so monitor your new arrivals carefully to ensure that they are not getting blasted with too much light. Gorgonians that are receiving excessive light will often not expand fully despite adequate flow, or will become overgrown with algae. Positioning your gorgonians in such a way that light and flow are "just right" can be a bit challenging, but once a balance is struck they tend to do well for a long time provided conditions do not change.
    III. Feeding
    Despite what much of the traditional wisdom involving these animals suggests, all gorgonians, photosynthetic or otherwise, are active planktivores and should be fed with some sort of dissolved micro-food on a regular basis. I feed mine Reef Roids and pulverized PE pellets, but any similar coral food will likely work just as well. Generally speaking the larger a gorgonian's polyps, the more it benefits from feeding; in fact some very large-polyped varieties (e.g. Eunicea) will even eat normal fish foods like whole pellets, flakes, or mysis shrimp. One or two feedings a week should be fine for most photosynthetic species, though more frequent feeding will stimulate rapid growth.
    During feeding, I recommend turning off your aquarium's circulation pumps and target-feeding each gorgonian individually using a pipette or turkey baster. All polyps in the colony share resources with each other, so don't worry if you don't get food to every single one. Leave your pumps off for ten minutes or so after feeding to allow the animals to eat, then turn on your powerhead or wavemaker for another ten minutes to circulate floating food particles throughout your display. It is best to keep your return pump off for the entire duration of the feeding to prevent food from being carried away into your filtration media. Just don't forget to turn the pump on again when the feeding is done!

    The large polyps of this Eunicea sp. are well adapted for catching plankton.
    As with any animal a varied diet is best, so combining microalgae/phytoplankton-based foods with zooplankton-based foods is always a good idea. The absolute best option would be to feed your gorgonians a combination of home-cultured live microalgae plus small planktonic animals like rotifers, copepods, or Artemia. We have a number of good growing guides here on N-R for culturing live foods in case you're interested in taking this extra step. 😉 @seabass's guide to culturing phytoplankton is a great place to start!
    IV. Water Quality
    Photosynthetic gorgonians are hardy by coral standards, but they still require a well-established aquarium with stable parameters. I do not recommend adding gorgonians to tank that is still cycling / might not be cycled all the way yet / has just finished cycling. Let things settle down and get into a normal, predictable rhythm before adding gorgonians to your system. "Dirty" water with lots of organic nutrients is often not that big of a deal for these animals (in fact having "zero" nitrates and phosphates is almost certainly bad for them), but it's important that parameters remain stable. The calcium, alkalinity, and nutrient levels in the average mixed reef aquarium are more than adequate for most photosynthetic gorgonians, so just aim for whatever levels work for the rest of your livestock and you should be okay.
    One element that bears special attention is iodine. The protein that gorgonians use to build their skeleton contains a considerable amount of iodine, and maintaining adequate levels of it (usually by supplementing it in the form of iodide) likely has a positive impact on their growth. Many smaller reefs have their iodine levels depleted rapidly, especially if they contain a variety of iodine-hungry soft corals and mushrooms, so supplemental dosing may be necessary to keep up with consumption. Just remember that excess iodine in the water is toxic to many animals, and too much can even kill the bacteria that make up your biological filter. It is therefore a good idea to keep careful track of iodine consumption and only dose as much as is necessary to keep your levels around 0.06 ppm (which is the concentration of natural seawater). Blind-dosing of iodine can be dangerous and is not recommended.
    That being said, most photosynthetic gorgonians can certainly be kept in low-maintenance setups that dose nothing at all, so long as a simple regimen of regular water changes is observed. Dosing iodine is simply an option to accelerate their growth.
    V. A Note on Sloughing
    Many species of gorgonians periodically shed a waxy film off their surface to prevent algae and other sessile organisms from colonizing their bodies. At the start of the shedding process a colony may close its polyps for a number of days or sometimes even weeks before sloughing off its outer layers. Don't be alarmed if this occurs in your aquarium from time to time, as it is a natural process that is essential for the proper health of your gorgs. If you notice ribbons of waxy gunk hanging off your gorgonians, try gently squirting them with a turkey baster to speed the process along. 
    3. Reproduction and Propagation
    Gorgonians in the wild can reproduce sexually by spawning, but the most common method of reproduction both in the ocean and in aquaria is asexual reproduction by fragmentation. In nature gorgonians are periodically pounded by storms and strong waves that scatter their branches about, and some even encourage this process by intentionally weakening their own branches or dropping little bits off of themselves. Each piece that lands in a favorable location has the potential to grow into a clone of its mother colony. 
    Many gorgonians sold in the aquarium trade are specimens that were propagated by fragmentation. For most photosynthetic gorgonians this process is quite easy: simply snip off a branch from the main colony with scissors, glue it down to a rock or reef plug with gel superglue or underwater epoxy, and place it in a suitable location in your aquarium. As long as conditions are right the fragment should establish a holdfast and begin growing fairly rapidly. The main colony should also regenerate quickly; in fact some species from the genus Antillogorgia have even demonstrated increased growth after injury compared to intact colonies.
    4. Aquascaping With Gorgonians
    Positioning gorgonians in your aquarium can be somewhat challenging, but when successfully incorporated into an aquascape they are breathtakingly beautiful. Photosynthetic gorgonians can be kept in practically any size aquarium, but tanks of at least 10 gallons are recommended as most gorgonians need to reach a reasonable size in order to demonstrate the full effect of their lovely branching growth patterns.

    Combining multiple species of photosynthetic gorgonians can make for a lovely display.
    There are a number of ways to incorporate gorgonians into your aquascape, and how you go about doing so will largely depend on your other livestock and the layout of your rockwork. With their beautiful swaying motions and soft, fuzzy polyps, gorgonians are an excellent way to provide movement and fill vertical space in your tank. They must however be given adequate room to sway in the current, and care must be taken to ensure that your gorgonians are not touching or rubbing against anything else in the tank, especially not other corals. Gorgonians of different species will usually sting each other if they touch, and even members of the same species will retract their polyps in places where they rub together. The sting of most gorgonians is quite weak, so they tend to lose coral wars with pretty much everything. Keep this in mind when positioning them in your tank.
    You'll also want to make sure that your gorgonians are oriented perpendicular to the current, and that they have adequate access to light. Many gorgonians grow quite quickly, so be mindful of their potential to eventually shade out other corals below them. Most gorgonians can be trimmed back without ill effects if excessive shading becomes a problem, but it's best to avoid this issue altogether by positioning them carefully from the get-go. All gorgonians must be attached to a hard substrate like a rock or a reef plug, so don't attempt to bury their bases in the sand. In addition each individual species of gorgonian has slightly different positioning needs based on the habitat in which it is commonly found in nature. Many Antillogorgia spp. for example like to grow horizontally out of vertical rock walls with their plumes reaching sideways into the current. Doing some research on the specific species you'd like to keep and orienting them accordingly can help increase their chances of success in your aquarium.
    5. Hardy Starter Species
    If you're interested in keeping photosynthetic gorgonians in your tank, several good entry-level options are detailed below. I have kept most of these species myself and have had good results with them so far.
    Antillogorgia spp. (formerly Pseudopterogorgia)
    Common names: feather gorgonian, sea plume, purple frilly gorgonian
    These beautiful featherlike gorgonians grow very rapidly under good conditions. They are usually some shade of purple, but yellow varieties are also available. Polyps are generally cream-colored or brown. Many species of Antillogorgia like to be oriented diagonally or horizontally, with the main axis sticking out sideways into the current. They do best under fairly bright light and can tolerate strong water movement. Algal growth can sometimes be a concern with this species, so keep an eye on them and make sure they don't become overgrown with cyanobacteria or diatoms. Use a soft brush or turkey baster to blow diatoms off their branches. Some species (e.g. A. bipinnata) can grow to a considerable size.
    Muriceopsis flavida
    Common names: purple plume, purple bush
    M. flavida is the first gorgonian I kept, and is one that continues to do well in my tank to this day. It has a beautiful purple color with very fuzzy brown polyps. This species can tolerate rather less water motion than others (though it does just fine with plenty of flow as well), so it may be a good choice for those with smaller aquariums or setups that require less flow.
    M. flavida seems to have an interesting habit of dropping the tips of its branches from time to time. I believe this is an example of propagation by intentional self-fragmentation. This freaked me out at first because I could not understand why pieces were falling off my otherwise-healthy gorgonian, but after months of observing this specimen I have decided that it's simply a normal behavior and is probably nothing to worry about.
    Pterogorgia anceps
    Common names: sea whip, ribbon gorgonian, cactus gorgonian
    This cactus-shaped, straplike purple gorgonian is one of the hardiest species around. It sheds an especially thick waxy film from time to time, which helps it resist algal growth in the shallow, brightly-lit waters it calls home. I have read reports of this species gradually declining over time in aquaria because it requires very strong light and needs robust water movement to assist with its heavy shedding regimen, but so far I have not had any problems with it myself. It is also notable for being a very sturdy shipper. This species seems to benefit greatly from supplemental feeding with fine planktonic foods, so don't forget to feed it once or twice a week.
    Another species from this genus, P. citrina, is also occasionally available in the hobby. It is yellow rather than purple, has thinner blades, and generally exhibits a more bushy, less elongated growth pattern. It is slightly more delicate than P. anceps but its care requirements are generally similar.
    Muricea elongata
    Common names: spiny bush gorgonian, rusty gorgonian
    M. elongata is an attractive orange or rust-colored gorgonian with projecting calyces (the small cuplike projections that house its polyps) that give it a spiny appearance. This species seems to like fairly strong indirect flow and moderate to bright light. It does not seem to shed very often at all (in fact I can't recall ever seeing it do so), but nonetheless appears to have no problems keeping itself free of algal growth. With its polyps extended it looks very attractive indeed. Muricea have a bit of a reputation for being poor shippers, but if they survive the first week or so in your system they are likely to do well for a long time.
    Another species in this genus, Muricea laxa, is also available in the aquarium trade. It has a beautiful silvery-white coloration with tan or brown polyps. M. laxa comes from deeper water and is much more rigid than the fairly flexible M. elongata. It is known to be a more robust shipper than other Muricea.
    Eunicea spp.
    Common names: sea rod, candelabra gorgonian
    Eunicea calyculata
    The genus Eunicea contains a number of very large gorgonians that can reach heights of more than a meter out in the wild. Most species have thick, cylindrical branches with large fuzzy polyps. They generally start out as single rods that begin to branch (usually in a single-planed candelabra pattern) as they get older. These gorgonians can handle a lot of water movement, but care must be taken to ensure that their long branches do not rub against their surroundings as they blow around in your tank. Growth can be quite quick once established, and colonies that get too large are easily pruned by simply cutting their branches with a pair of scissors. The resulting fragments can be glued down to a piece of rock or a reef plug to propagate the colony. Eunicea seem to ship fairly well, with the exception of one species: E. flexuosa (formerly Plexaura flexuosa). E. flexuosa is a gorgeous gorgonian, but has a tendency to get quite brutalized in shipping. Mine lost multiple branches and took a month to settle down after being added to my tank, which is an extremely long time by photosynthetic gorgonian standards.
    Pinnigorgia flava
    Common names: Grube's gorgonian

    A beautiful Grube's gorgonian from N-R member @lizzyann's mixed reef aquarium. Photo from her aquarium journal.
    Grube's gorgonian is one of the few photosynthetic species from the Indo-Pacific that is commonly available in the hobby. It has a bushy growth pattern and seems to grow very rapidly under favorable conditions. I have not kept this species myself, but several gorgeous reef tanks here on Nano-Reef feature this species so I think that it bears mentioning here. It seems to be quite hardy and has fairly standard care requirements for a photosynthetic gorg. Grube's gorgonian has been popular in Europe for some time, but has only reached American markets relatively recently.
    6. TOTM Gorgonian Gallery
    Looking for some great examples of beautiful reef tanks that highlight photosynthetic gorgonians? I've included a few of my favorites from Nano-Reef's Tank of the Month (TOTM) archive below! Many of these systems have given me a lot of inspiration, so I hope they will do the same for you.
    (Sorry for not tagging everyone; some folks from older TOTMs have since changed their name and no longer show up on a tag search 😅)
    @yardboy's 10 gallon Florida biotope (September 2008)
    trueisb2's 20 gallon nano reef (September 2012)
    Ziareefer's 50 gallon seahorse and gorgonian tank (February 2014)
    trueisb2's 3.5 gallon pico (March 2014)
    @Felicia's 40 gallon predator tank (December 2015)
    @kimberbee's 10 gallon gorgonian & RFA tank (May 2017)
    @Sharbuckle's 40 breeder (October 2018)
    References and related reading:
    Sprung, Julian and Delbeek, J. Charles. The Reef Aquarium, Volume II. Ricordea Publishing, 1997.
    Sprung, Julian. "Aquarium Invertebrates: Caribbean Gorgonians: Beauty in Motion." Advanced Aquarist, 2004. 
    Moore, Morgan. "Photosynthetic Gorgonians for the Home Aquaria." Reefbuilders, 2013. 
    Messing, Charles G. et al. "South Florida Ocotocorals: A Guide to Identification."
    Marine Depot
    Let’s talk about the difference between fresh and saltwater algae scrubbers.
    They are different designs because the algal growth you get in each are different—so the layout of the scrubbers needs to be able to handle this. Freshwater growth tends to be mostly Spirogyra or Cladophora species, which are very long (one meter) and very thin, like a string or thread.

    This super-long growth means two things: First, it’s going to try to flow with the water flow, which can be a very long pathway. And second, if the growth lets go, there is going to be long strings of growth finding their way into aquarium plumbing, pumps, etc. Since many freshwater people put the scrubber in their display (because they don’t have a sump) this long growth can get all over.
    A plus for freshwater is that many of the fish that people keep (guppies, goldfish, plecos, etc.) love to eat this algae, so it can be an endless source of fresh free food. As a matter of fact, it’s relatively easy to have a freshwater tank that needs no outside food or water changes at all, and yet still has low nitrate. And the fish get to eat what they love the most.
    Long freshwater growth is fine if your scrubber and installation are set up for it. Generally, you don’t want a waterfall style for freshwater because the long growth flows right down the drain with the water flow—and can extend for a meter past that!

    If it’s a waterfall in a sump, this growth will get caught up (or will clog) the return pump. And you can’t really put a waterfall over a display, so it must go in the sump. Thus waterfall designs are not recommended for freshwater.
    READ  Algae Scrubbers Explained: Natural Filtration For Your Aquarium – Marine Depot Chats with Experts #7   Upflow designs however are particularly suited to freshwater:
    Upflows are easy to DIY by using a common air pump which many people already use for freshwater. Freshwater people usually want bubbles. Many freshwater tanks have no sumps, which is no problem for upflows because upflows can go into the display. Since filter units in freshwater usually go in the display, the fish can pull the algae out and eat it. The long growth is circulated around (and held) inside the upflow container, keeping most of the growth from clogging other filters or pumps.  

    Now let’s look at saltwater.
    The big difference with growth in saltwater is that it grows much coarser and thicker strands (Ulva species, etc.) which tend to be curly but also much shorter than freshwater. So you no longer have to deal with long growth that grows out of the filter. This means that any version of a scrubber will work: upflow, waterfall, or horizontal river. But with saltwater you do have to deal with thick growth that blocks light.
    The concept of blocked light is important because algae will die when light blockage occurs. Dead algae cannot hold on, so it washes away, and there goes your filter. It’s ironic: Thicker growth seems great, but it blocks light, which kills the growth. Dead growth is brown like hay and can give water a yellowish look.
    So what should you do?

    Fortunately the growth does not die right away. It takes a few days once the light has been blocked. So if you clean/harvest before the “roots” die and let go, you are good (algae do not really have roots but do have holdfasts which grab solid surfaces).
    There are some tricks to getting more growth before die-off occurs. You might think you can simply reduce the hours of light so it does not grow thick so quickly, but this reduces filtering and thus defeats the purpose, not to mention it give more hours of darkness which does not help the roots. So the idea is to grow fast but not shade the roots too soon.
    Here are some things to look for or try:
    A waterfall or upflow screen should be illuminated on both sides so the roots that are grabbing the screen get light from both sides. This will let the growth go several more days before the roots get zero light.
    Adding strings to a screen or a solid surface lets the growth grow away from the screen or surface, thus getting the roots out of the darkness. Strings by nature are already 2-sided.

    Usually the middle of a screen is where growth is the thickest and die-off occurs first. By using very strong light in the middle of the screen, this area can be kept un-grown until an outer ring grows first, thus keeping the middle alive longer. The term for this is “photoinhibition.”

    By letting your animals eat some of the growth, the time for the growth to get too thick will be lengthened. It’s possible the growth will never get too thick with this approach.

    Instead of letting the growth go a full 7 to 14 days before cleaning, you can clean half of it every 3 to 7 days. Since you are cleaning / brushing / scraping right down the middle of the growth surface, this opens the middle to more light.
    A more elegant way of doing alternate cleanings is to divide the growth surface in half, and clean each at alternate times. A waterfall screen is easily cut vertically for this.
    The “most” elegant way of achieving alternate cleanings is to have multiple scrubber units. This achieves the same growth time for each growth area as above, but you do not have to deal with taking/leaving part of the growth behind, and you also do not tear growth in half which can put little bits of growth into the water. It also is the most expensive way.

    Santa Monica Filtration HOG2x Freshwater Hang-On-Glass Upflow Algae Scrubber
    Remember, the above information is for after a scrubber has been growing, or after you get through a slime stage. No scrubber will look or perform like this when brand new. For an example of a modern freshwater scrubber, here is a high power HOG2x with extra light for high nitrate water.
    Happy Scrubbing!
    The Complete Guide to Algae Turf Scrubbers: Part 1 The Complete Guide to Algae Turf Scrubbers: Part 2 The Complete Guide to Algae Turf Scrubbers: Part 3
    Marine Depot
    Now let’s answer the first question most aquarium folks have about algae scrubbers: Should you buy or build?
    Before the year 2010, there were not really any commercially available algae scrubbers available for purchase.
    Fast-forward to today: Now you can buy tiny-to-medium size algae scrubbers in the upflow style as well as medium-to-large sizes in the waterfall styles.
    In terms of doing it yourself (DIY), there are discussions on aquarium message boards that detail just about every algae scrubber that anyone’s even attempted to build—complete with growth examples and nutrients measurements completed over time. There are some truly amazing DIY scrubber builds out there.
    We won’t go too deep into specific DIY plans in this article, but there are many available online. You may even find some on this very forum! If you’re super curious, you can check out builds going back 20 years on AlgaeScrubber.net.
    A DIY algae scrubber can be made fairly easy if you are skilled in building stuff. The typical materials of PVC pipe, acrylic sheet, glue, airline tubing, etc. are needed, just as if you are building a DIY reactor, overflow, or sump.
    One difference with algae scrubbers, however, which makes them a bit more difficult, is the lighting that’s needed for the growth. Not only are you now dealing with electricity, but unlike DIY display lights which are above the tank in a dry air environment that you rarely touch, the lighting for an algae scrubber is in a humid or wet environment (or even underwater) that you touch daily—with wet algae dropping on top of it—all while possibly standing on a wet floor (maybe even with bare feet).
    Long story short, you probably won’t want to make a complex algae scrubber your first-ever DIY project!
    Some advantages of buying a scrubber are that you obviously don’t need the time or space to build one. But other reasons are that it’s hard to DIY some types of scrubber designs, even if you are good with DIY. Things like underwater lights for upflow scrubbers, or gravel-epoxy surfaces for algal attachment, or the long slot in a waterfall pipe, takes a few tries to get it right (meaning your first try will probably not work).

    Buying a pre-built unit, however, is limited to what is for sale. Currently the only models available are waterfalls (which Santa Monica Filtration invented in 2008 and are now made by SMF and others) and upflows (only made by Santa Monica Filtration), and these are in certain sizes only.
    There are a very few number of horizontal river models. However, these come from China and are tiny without any lights. And there are no dumping bucket designs available at all, probably because of their complexity.
    The biggest advantage of DIY is, of course, saving money.
    Most $300 commercial models can be DIY’d in a week for $60 in parts, and most of the costs is in the lighting. But DIY also lets you choose the exact style, size, and layout you want to fit into your exact space. If you need a very large model, such as for small exhibits at public aquariums, you will have to DIY.
    DIY waterfall styles are generally going to need some acrylic or plastic gluing, unless you can find the proper size plastic box to start with. Cutting the slot in the waterfall pipe is the hardest part, and although it can be done with a Dremel moto-tool cutoff wheel, most people end up doing it over again with a table saw, router, or other shop equipment.
    The lights are easy. Usually low cost Chinese plant-grow lights can be used from eBay, as long as you follow safety steps properly. Most DIY folks can do the PVC pipes, so that’s not a problem. Waterfalls are not really suitable for freshwater because the growth gets long and clogs drains and pumps. Also, waterfalls work best when placed over a sump — not externally on their own — because they can overflow, leak, and also drip from the waterfall pipe.

    DIY bubbling upflow styles can be the easiest if they are similar to the Hang-On-Glass styles that Santa Monica Filtration makes.
    These styles need no acrylic gluing or PVC pipe. The LED lights just stick to a plastic cover on the outside of the sump or tank wall using magnets or suction cups. The airline tubing for the bubbles is as easy as a goldfish tank. Cheap LED lights and a power supply from Ebay will do because they stay dry and are low voltage (no 240/120 volts at the light).
    These designs might be suitable for first-time DIY projects if you can get help with the lights and are great for freshwater too because the long growth is kept mostly inside the growth compartment. Lastly, they can’t overflow, leak, or drip because they are already underwater.
    DIY horizontal rivers are relatively easy to build — at least the river water part is. But again, the lighting can be a challenge over the long narrow pathway. One workaround for this is to put it under your display lights, but that’s too cumbersome and unsightly for most people. And if you put it over a sump, these designs tend to cover the top of the sump like a lid, so you can’t get access to anything.

    If you have multiple tanks, a good piece of advice is to first try a scrubber on the smallest aquarium. Especially if it is freshwater, because that way you can get a feel for placement, lighting, cleaning, noise, etc. before working up to a bigger one.
    Meanwhile if you want to take a look at modern algae scrubbers, here is a Santa Monica SURF2 floating model — shown below floating in a saltwater reef pond.

    Happy Scrubbing!
    If you missed the first entry in this series, read The Complete Guide to Algae Turf Scrubbers: Part 1 to learn more about the history of algae scrubbers. 
    Marine Depot
    Filtering your tank by using “algae to fight algae” has been gaining in popularity in the last few years. We are biased about this, because we invented the waterfall and upflow designs that everyone uses now, but nevertheless we wanted to make this in-depth series about everything, including:
    History of algae scrubbers DIY topics Commercial models Comparison to other filters Usage with other filters Sizing Lighting Water flow Operation Fresh vs. Saltwater Effects on animals Troubleshooting Dosing Types of algae Results in tank Uses of algae Safety

    First, the origin of scrubbers should be mentioned. It was Dr. Walter Adey of the Smithsonian Institution in the USA who really got the scrubber concept going in the 1970’s, when he was investigating nutrients and corallines on reefs.

    His nutrient measurements confirmed what other researchers had found, which is that nutrients basically “stay on the reef” and do not flow out into the ocean, even though the water itself flows out into the ocean. It was already known back then that reefs are both generators and consumers of nutrients, consuming any nutrients as soon as they were available (thus making reef water “nutrient poor”), but he wanted to investigate further into who generated and consumed what, and how much. He started publishing many reef nutrient studies, and came out with the first edition (now in third edition) of his Dynamic Aquaria book which describes in great detail about nutrient flow in reefs, corals, algae and animals.

    Adey’s big contribution to the aquarium community was in the separation of the nutrient generators from the nutrient consumers. The generators are the animals, micro creatures, and bacteria that all generate ammonia, whereas the consumers are the algae which consume this ammonia. On reefs this is all intermixed and it keeps nutrients inside the reef, but he separated out the algae and created a device which mimics the environment where the most biomass of algae grew the fastest, where waves crash down on rocks. As soon as you scraped algae off of these rocks, it could be fully regrown in just 24 hours, and that’s even while teams of herbivores were eating it. This could be a 100x increase in biomass in 24 hours, which absorbs a tremendous amount of nutrients from of the water.

    Photo from algalturfscrubber.com
    His device in 1980 used a dumping bucket to pour water onto a very shallow screen, and thus made a bubbling turbulent air/water interface that grew a lot of biomass of algae fast, and he called this device a “turf scrubber” because it grew a turf algae and it scrubbed (removed) nutrients from the water. By separating the nutrient producers from the nutrient consumers, the conditions for operation of the consumers can be controlled and optimized without changing the conditions for the rest of the reef (aquarium) itself.

    Adey licensed the design to someone to have some small models made, but nobody ever really sold many of these dumping bucket designs because they were so big, complex, splashy and noisy, and also they were just 1-sided (top side) only which grows less. Also, Adey never had any interest in making or selling them himself, so they disappeared.

    Later in the 1990’s a few people made and sold the simple horizontal river design, like the Aquaricare scrubber which had little baffles to stir up the water and create a more turbulent air/water interface (the light on top is removed for the photo). But it too was large, splashy, hazardous (used high voltage T5 bulbs and wiring), and was also just 1-sided (top side) which meant it had to be larger to make up for less dense growth.
    And so, up until 2007 the basic algae scrubber designs were the dump bucket, horizontal river, and rotating wheel. And none were really being sold, so nobody know about them.
    Then came “Santa Monica” (us!) on the forums in 2007, with the first waterfall style scrubber. The thinking was that there must be an easier way to get a turbulent air/water interface on a screen than using a bucket, a wheel, or a river. Let gravity do the work straight down! And a waterfall on a screen could have lights and growth on both sides, so it would grow more and could be half the size. This first waterfall was put into a bucket on a sink in the office, complete with dangerous CFL bulbs that got shorted by salt spray. This was all posted on various forums as “Waterfall Turf Algae Filter: CHEAP and EASY to build” if you want to read it.
    It grew great, and brought nutrients down to zero with no water changes. But in order to get a waterfall in to our sump area it would have to be low-profile, so a custom acrylic box was made and the Santa Monica 100 was born (100 was for 100 gallons).

    This was the first model to sell any real amounts. But it had flaws which caused it to be left behind in favor of our modern versions. First, it could not reliably be mounted anywhere but over a sump, because a clogged drain would cause an overflow onto the floor, or a clogged slot would cause water shooting out the top, even with a lid. Second, the cleaning/harvesting process was very involved, requiring water shutoff and disassembly of some plumbing or even taking the whole scrubber out. Third, the acrylic was fragile and easily cracked, especially after many heating/cooling cycles. And lastly, the high voltage 240/120 volt metal-case lights were dangerous for non-DIY users who just wanted a safe product. The lights would slowly corrode in the salty environment, and eventually short out.
    And so there you have it: the evolution of the algae turf scrubber from the 1970s to today. We’ll get into many other topics, but for now we’ll just link to one of our smaller modern models, the HOG1x, which is a great “starter” scrubber.
    Culturing Phytoplankton
    Live microalgae is a natural food source used for feeding clams, sponges, soft coral, and other filter feeders.  It's rich in Omega-3 fatty acids, carbohydrates, lipids, and plant sterols.  As the foundation of the aquatic food chain, phytoplankton (phyto) provides food for zooplankton, which are then eaten by: stony coral, planktivores, and other invertebrates.  In addition, pods that feed on microalgae are more nutritious prey than pods which feed on detritus.
    When we talk about phyto, we are usually referring to one or more of the thousands of species microalgae.  However, phytoplankton also includes other protists, including cyanobacteria and dinoflagellates.  For this article, phyto will mean microalgae (including diatoms, which are a type of brown microalgae that is often included in live phyto blends).
    Live phyto blends, containing various species of microalgae, are available from local and online retailers.  Some of these products are filtered and concentrated.  However, the nutritional value of these cultures will still decrease when refrigerated, and cost (especially considering next day shipping) can become prohibitive.  In this article, I will discuss how to culture your own phytoplankton.
    Nannochloropsis oculata
    I am currently culturing the microalgae species, Nannochloropsis oculata.  It's often used to culture rotifers due to its high levels of vitamin B12 and Omega-3.  And while it's beneficial to copepods, larvae, and filter feeders, it has a relatively thick cell wall which makes it harder for certain animals to digest.[1]  Another species might be even more suitable if exclusively culturing phyto to raise copepods.
    I started my culture using AlgaGen PhycoPure Greenwater (Nannochloropsis) which I purchased from Live Aquaria.  AlgaGen claims that customers have reported good results feeding Nannochloropsis to rotifers, copepods, amphipods, corals, shrimp, feather dusters, clams and other filter feeders.[2]  Plus, it's pretty easy to culture.
    Florida Aqua Farms is another good source for a starter culture.  They also sell f/2 fertilizer, which has been used to culture microalgae for over 30 years.[3]  Live phyto blends purchased from your LFS can be used to start a culture; however, this will likely result in a monoculture of a single species (often Nannochloropsis).  Finally, a starter culture can come from another reefer who is culturing phyto (so check with your local reef club).
    Phyto Culture Containers
    Most commonly, hobbyists use one or more clear plastic two-liter bottles to culture microalgae, but you could use any size clear bottle with a cap.  I'm currently using two one-gallon Hawaiian Punch jugs.  Using two bottles helps ensure sustainability should one of the cultures crash.
    Simply drill a hole in the cap for the airline tubing, leaving a little room for air to escape (to avoid the build up of air pressure, which could affect air flow).  I used a ¼” bit, which seems to work fine.  I have read where people have used filter floss to cover open gaps; but with a ¼" hole, this really isn't necessary.
    I didn't bother to sterilize the bottles; I just rinsed them out.  However, I've read where others recommend sterilizing them prior to use.  Actually, I don't usually sterilized my containers or other equipment unless I'm doing a deep clean.  I do, however, try to keep everything rinsed clean and free of contamination from tank water.  Also, I make sure that none of the equipment which I use to culture rotifers is used for growing phyto.
    Specific Gravity
    Although most phyto species are pretty tolerant to various specific gravities, it's commonly recommended to culture phyto at 1.020 sg.  Likewise, rotifer cultures can tolerate a relatively wide range of salinities; however, they tend to be most productive between 1.014 and 1.017 sg.[1]  So if you are culturing rotifers, you might wish to culture your phyto using a lower specific gravity.  I'm currently culturing both my rotifers and phyto at 1.019 sg.
    Always use new saltwater for your phyto cultures (never use water from your tank).  Contamination from tank water, or from a rotifer culture can compromise your phyto culture.  A ⅜ cup scoop of salt mix should make a gallon of saltwater with a suitable specific gravity.  I'm using a scoop that was included with some protein powder.  These scoops come in various sizes, so test it first (mine mixes one gallon of RO/DI water to 1.019 sg).  But just like in a reef tank, a specific salinity isn't as critical as consistency.
    Dosing Nutrients and Trace Elements
    Nitrate and phosphate are needed to grow microalgae; but trace elements (like iron, copper, zinc and manganese) are needed too.  In addition, brown/tan microalgae (diatoms) need silicate.  In order to supply our cultures with these elements and nutrients, we dose fertilizers with trace elements.
    When starting a new culture or splitting an existing culture, add 1.5 ml of Guillard f/2 fertilizer for each two-liter bottle.  I recommend using Micro Algae Grow from Florida Aqua Farms.  However, it's possible to use Miracle-Gro Liquid All Purpose Plant Food by adding Kent Essential Elements.  But I'm not exactly sure of the correct dosages, and Miracle-Gro might contain ingredients and/or quantities that are not ideal for reef tanks.
    Dosage notes: 20 drops is roughly equal to 1ml.
    Use 3 ml (60 drops) of f/2 per each gallon, when starting or splitting a culture. Use 1.5 ml (30 drops) of f/2 per each two-liter bottle, when starting or splitting a culture. Use ¾ ml (15 drops) of f/2 per each liter, when starting or splitting a culture. Use ⅓ ml (7 drops) of f/2 per each pint, when starting or splitting a culture. Aeration
    Aeration is necessary to supply carbon dioxide for photosynthesis and to help maintain pH.  However, excessive aeration can potentially fracture the cells and cause foaming.[1]  Air stones aren't necessary, but I have used them with Nannochloropsis in the past without problems.  Instead of air stones, most people recommend using rigid air line tubing.  In addition, you'll need an air pump, flexible air line tubing, a gang valve, and a check valve.
    Aeration also circulates the non-motile algae, which exposes the individual cells to the light and helps prevent them from settling to the bottom.  You can occasionally (like once or twice a week) gently shake the culture(s), but this generally isn't necessary.  I have an extra cap (without a hole in it) in order to shake my bottles without spilling the culture; but you could just put your finger over the hole in the cap instead.
    Room temperature is typically fine.  Plus, you don't want to use incandescent light bulbs for lighting, as they may heat the culture too much.
    I originally used compact florescent work lights, but I had one melt down and nearly caused a fire; so I switched to a plastic clamp-on light with a standard 75W equivalent LED light bulb (daylight spectrum).  I leave the light on 24/7, but 16 hours a day would be adequate.  Try to light the side of the bottle(s), versus just the top (which is smaller and partially blocked by the cap).
    Harvesting Phyto Weekly
    I keep the culture going by harvesting it weekly as follows:
    Make enough new (1.019 sg) saltwater to dilute your culture in half (one gallon in my case); then let the salt mix dissolve thoroughly. Pour half of the culture to be harvested into a bucket with the fully dissolved saltwater (this will be your new diluted culture).  The other half can be used to dose your reef tank(s), maintain a pod culture, or stored for future use.  You can optionally remove larger particles from the culture by pre-straining it through a 53 micron plankton sieve (available through Amazon).  Nannochloropsis is only about 4 to 6 microns in diameter.[1] Clean the culture bottle(s) with a bottle brush.  If needed, you can use vinegar to help clean it.  A bleach solution could also be used to clean and sanitize the bottle (just make sure that you thoroughly rinse and dechlorinate it afterwards). With the help of a funnel, pour the newly diluted culture back into the clean culture bottle(s). Add 1.5 ml of f/2 fertilizer into each two-liter bottle (or in my case, 3 ml into each one-gallon bottle).  
    Harvest your cultures once a week. Foaming on top of the culture can indicate that harvesting is overdue. If using more than one culture bottle, you could potentially harvest them on different days. When starting a new culture, it might look fairly pale in color.  If so, let it darken up before you start harvesting it.  However, you should continue to add f/2 weekly (and give the culture a gentle shake).  You'd be surprised just how small of a phyto sample is required to start a new culture. Storage
    Freshly harvested phyto provides the best nutrition.  However, it's possible to store it when necessary.  Use (clean) empty water bottles to store harvested phyto in a refrigerator.  Label them with a date so that you know how old they are, and so that nobody mistakes it for something else.  You can keep phyto in the refrigerator for up to a month (keeping in mind that its quality will continue to degrade with time).
    Dosing Phytoplankton
    Gently shake or invert the refrigerated phyto bottle at least once a week, and before dosing.  You can either broadcast feed your tank, or target feed specific specimens with the help of a clean syringe, pipette, or eye dropper.  I suggest target feeding any livestock that requires phytoplankton.  This can be done by releasing the phyto a couple of inches upstream from the target.  When using a pipette (or another tool) to feed, avoid contamination of your phyto by pouring it into another container first.
    To broadcast feed your tank, start slowly.  Dose it into a high flow area of your tank.  Eventually you can increase the dosage and/or frequency.  It has been said that excessive dosing could negatively affect water quality, but I haven't found that to be the case.  Still, it's a good idea to monitor your tank's nutrient levels when you first start dosing, or if you change how much you're dosing.  I might start dosing a few milliliters per gallon each week and adjust from there.  It's not unusual for me to dump an entire liter of phyto into my 40 gallon tank (which is enough to tint the water green).
    Water Quality
    I tested my phyto culture for phosphorus just prior to harvesting it by diluting a sample with 9 parts of clean saltwater. Through that, I determined that the undiluted phosphorus concentration was 310 ppb (or roughly 0.95 ppm of phosphate), which was actually lower than I had expected.
    There are about 3,785 ml in a gallon, so dosing 1 ml per gallon would cause an immediate increase in phosphorus of just about 0.08 ppb (or about a 0.00025 ppm increase in phosphate).  That's really not that much phosphate.
    Nutrient Consumption
    AlgaGen states that Nannochloropsis, “is also known to be a great water conditioner” consuming and binding nitrate, phosphate, and heavy metals.[4]  This is contrary to phyto's reputation for adding phosphate to your tank (which, as I indicated above, it initially does).  However, I assume that the live phyto continues to consume nutrients within our reef tanks after dosing, potentially lowering nutrient levels (versus raising them).
    Wilkerson, Joyce D.. Clownfishes. Microcosm Ltd.. Kindle Edition. https://www.liveaquaria.com/product/3249/phycopure-green-water http://floridaaquafarms.com/ https://www.algagen.com/phycopure1.html
    Setting up your first nano reef is an exciting endeavor! Not only will you now have a piece of the reef in your home, but also an interesting new hobby and challenge. When setting up a nano reef or any saltwater aquarium in general, it is important to do your research ahead of time in order to create a tank that you and the tank inhabitants will enjoy. In this article I will cover basic information regarding what you will need and what you should do in order to create the tank of your dreams.
    General knowledge of the reef:
    Before you start to set up your aquarium it is important to know what you are getting into. Keeping a nano reef can be quite pricey and time consuming at times. Before setting up a tank be sure to make sure you have the time, money, and commitment to keeping an aquarium. Despite the previously stated, keeping nano reefs can and will be an amazing experience. 
    What you will need:
    Before you can dive into keeping a nano aquarium you must collect some supplies first. Remember that in reefing you get what you pay for so be sure to purchase quality products. Research your purchases in advance here on the forums to see how other hobbyists review them.
    Here is the bare minimum of what you will need:
    Powerhead or wave maker
    Thermometer Refractometer 
    Quality reef lighting
    Sand (unless you are going bare bottom)
    RO/DI water or distilled water
    Reef aquarium salt mix (may not be needed if you have access to natural sea water) 
    Live rock
    Below are some things I recommend, but are not absolutely necessary:
    Aquarium lid or screen cover
    Purigen, carbon, or other filter media
    Automatic top-off system for evaporation
    Sump for external filtration
    Protein skimmer
    Backup heater
    Extra tank and supplies for quarantine
    Basic medications (if you plan to keep fish)
    Getting started:
    Finally you have everything you need and are dying to set up your aquarium! I highly recommend leak testing your tank before setting it up, just use tap water for the test. Once your tank is drained from the leak test you'll be ready start by adding live rock to your tank in a way that is visually appealing, but also that is sturdy. Some people recommend placing the rocks on plastic egg crate grids to make them more stable. Be sure to leave enough space between the rocks and the sides of the aquarium for easy cleaning. Next, add your live sand (if you are adding sand)  to about 1.5 to 2 inches of depth. After adding the sand, begin to add your heater, filter, etc. but do not plug them in yet. Now, begin to add saltwater pouring it in slowly in order to avoid extremely cloudy water from the sand. If you are not using pre-mixed saltwater you will first need to mix in the appropriate amount of reef salt with RO/DI or distilled water before adding it to the tank. Finally, plug in the appliances and wait for the sand to settle. You’ve successfully set up your first nano reef!
    Common errors:
    Some of the most common mistakes in keeping a reef aquarium are moving to fast, not doing enough research, and not setting their tank up correctly. Remember keeping an aquarium is not a race or a competition so take your time and move slowly. The most common advice given on starting a nano reef is to research, research, and research, then to research more. This advice should not be taken lightly and can help to ensure you piece of the reef stays happy and healthy all the time. The simpler mistakes in nano reefing are things within the tank setup. Remember to make sure your heater is working all the time and that the temperature is not fluctuating. Another good thing to do is to test your salinity and water parameters at least weekly if not more. When placing your powerhead or wave maker in the tank make sure it is facing slightly down without stirring the sand, but rippling the surface of the water. This allows for the proper oxygen exchange that is vital for all sea life.
    Cycling the tank:
    An important thing to remember after setting up your tank is to let the tank cycle before you anything to your tank. Yep, I mean everything: no snails, crabs, or fish until the tank is done cycling. A brief summary of cycling your tank is that the tank is going through the nitrogen cycle. The tank will produce the toxic ammonia, convert the ammonia into nitrites, and finally convert the nitrites into less toxic nitrates. When you have zero ammonia, zero nitrites, and under ten nitrates it is safe to assume your tank is done cycling.
    Finding a good aquarium store:
    Before you can start adding things to your tank you should find a quality aquarium store where you can go for advice as well as livestock. You should look for a store that is under a hour away from you with good reviews. The store should be clean with healthy looking livestock and friendly staff member that are willing to provide strong advice regarding your nano reef. If there are no stores like this in your area buying online is always an option. Please note that if you choose this option there will be an additional cost for shipping and you will need to home for delivery. Some of my favorite online stores are, Cultivated Reef, Vivid Aquariums, and Live Aquaria.
    Adding your first inhabitants:
    So your tank has cycled and you have found a quality source for livestock. You are ready to start adding livestock to your tank! I like to add things like snails and crabs first, then fish, and finally coral. Be sure to not overstock your tank and to only add at most two things per week. Furthermore, it is not recommended to add 6 fish into a 10 gallon tank all at one time. Not only is that way to many fish for such a small tank, but they were also added all at once. You should also stick to beginner fish/corals/inverts to start. Here's a list of easy inhabitants to start with:
    Royal gramma
    Soft corals
    Emerald crabs
    Hermit crabs 
    Maintaining the reef:
    Your tank has finally been set up and has been thriving for the past few week to months. It is important to continue to move slow and do your research. Make sure to complete partial water changes at least every 2 weeks if not more often, and to test your water regularly. Also be sure to monitor your tank for any signs of disease or weakness. And most importantly enjoy your magnificent piece of the reef.
    Happy reef keeping!!!!!! 
    - Livia and a special thanks to ffoott
    Introduction to Pico Jar Maintenance: Water Changes
    Pico jar reefs seem to be gaining popularity with reef hobbyists. Maybe it’s a fascination with small things, or perhaps it’s the idea of “less work” that is appealing to some. For me personally, it’s a combination of the two. I love miniature versions of things, and I love the challenge of creating a miniature reef system, which just so happens to translate into less time spent maintaining the system and more time spent looking at and enjoying the system.
    For a basic pico setup with only a light source, heater, and circulation pump, the weekly water change is of utmost importance. It is the way you will remove the organics from the water and replenish lost minerals and trace elements. It is recommended to do a 100% water change removal and replacement. It is easy and safe to do, as well as cost effective, on such a small system.
    Standard Water Change Rules Apply
    Whether you are working with a 250 gallon system or a 2 gallon system, the standard water change rules apply. You will want to use RO/DI water (or distilled water) to help avoid nuisance algae. You will need to match your clean water salinity and water temperature to the pico system you are maintaining. You can use any salt mix that you like, but it is best to stick with one brand of salt as not all are created equally and switching salt frequently can be stressful to your tank inhabitants.
    Tools Needed

    Items I have found useful during a water change include: Towels, tubing or hose lines, algae scraper, tongs, scissors, turkey baster, 2 buckets.
    Since you need to work fairly quickly when doing a 100% water change on a pico reef system, it’s best to have everything ready before you get started.
    Let’s Get Started
    You want to have your corals exposed to air for the least amount of time as possible. While most coral can survive extended periods of time exposed to air, I still like to work as quickly as I can, while also being careful and thorough, with the task at hand. I start with scraping the glass for algae. This gets the algae suspended in the water column before water removal. Now that your glass is clean (let’s hope it wasn’t THAT dirty), you can observe any problem areas. You can use your tongs to pull out any hair algae/nuisance algae. This is also the time to look for any coral warfare that you may need to intervene in. Coral scissors/clippers may be needed for trimming or removing coral over-growth. In such a tiny space, coral growth will be even more obvious. Typically coral cutting makes the corals slime up. You want to do any cutting prior to water removal so that you can remove the slime with the water change.

    Now is the time to put that turkey baster to work! Blast the rocks and in between the coral to get any detritus suspended in the water column. You’d be amazed at the amount of detritus produced by the coral alone. 

    It’s almost time to drain your pico, but first, don’t forget to shut down your heater and circulation pump. You do not want to damage these items during the 100% water change.

    I find it best to have two buckets. One for waste water, and one for clean saltwater. Use your clear tubing and siphon the water out of the pico tank and into the waste bucket. I find it useful to do another basting of the rocks just prior to siphoning. You want to get as much detritus suspended and out as possible. Pay attention to the sand as a lot of detritus will settle in that area.

    Once all of the water is removed, all that's left is to replace the old water with the new saltwater that is temperature and salinity matched. Don’t forget to turn your air circulation and heater back on at the end. You can use your towels to clean up any spills.

    Final Thoughts
    While no system comes without work, I have found that maintaining a pico reef is easy, fast, and enjoyable. My main goal is to work as quickly as I can so that my coral is not exposed to air for an extended period of time. I find that planning ahead is very helpful to accomplish this goal. Have all of your supplies ready before you begin. It may sound scary to remove all of the water from your aquarium, but it is completely safe and successfully done by many hobbyists, including myself. You may find that it is so easy, and that you enjoy it so much, that you end up doing more than one water change per week. Quite frankly, it’s been known to happen.
    Happy pico reef maintenance, to all!
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