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  • Culturing Phytoplankton For Reef Aquarium Food

    seabass

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    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, 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 phytoplankton (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 may still decrease when refrigerated, and cost (especially considering next day shipping) can often become prohibitive.  In this article, I will discuss how to culture your own phytoplankton.

    Nannochloropsis oculata

    072318b.jpg.gifI 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 also beneficial to copepods, larvae, and filter feeders, its relatively thick cell wall can make it harder for certain animals to digest.[1]  Another species might be more suitable if you are specifically culturing copepods.

     

    I started my culture using AlgaGen PhycoPure Greenwater (Nannochloropsis) that 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 as 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 (check with your local reef club).

    Phyto Culture Containers

    072318e.jpg.gifMost commonly, hobbyists use one or more clear plastic 2 liter bottles to culture microalgae.  I'm currently using two 1 gallon Hawaiian Punch jugs.  Simply drill a hole in the cap for the airline tubing, with a little room for air to escape (to avoid a build up of air pressure which could affect air flow).  I used a 1/4” bit, which seems to work fine.  I have read where people have used floss to cover open gaps; but with a 1/4" hole, this really isn't necessary.

     

    I didn't actually drink the Hawaiian Punch, so I just rinsed out the bottles after pouring it down the drain.  I didn't bother to sterilize them, but have read where others have recommended it.  Actually, I don't regularly sterilized my containers or other equipment.  I do, however, try to keep everything clean, and prevent contamination from tank water.  Also, I make sure that any of the equipment that I use for rotifers isn't used to culture phyto.

    Specific Gravity

    072718a.jpgAlthough most phyto species are pretty tolerant to various specific gravities, it's commonly recommended to culture it 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 3/8 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.  Those scoops come in various sizes, so test it first (mine mixes 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) would need silicate.  In order to supply our culture these elements and nutrients, we dose fertilizer with trace elements.

     

    When starting a new culture, or splitting an existing culture (for each 2 liter bottle), I'll add 3ml of Micro Algae Grow (Guillard f/2 formula) from Florida Aqua Farms.  I recommend using Micro Algae Grow, but it's possible to use Miracle-Gro Liquid All Purpose Plant Food by adding Kent Essential Elements.  However, Miracle-Gro might contain ingredients and/or quantities that are not ideal for reef tanks.

     

    Notes: 20 drops is roughly 1ml.  Use approximately 1.5ml of f/2 fertilizer per liter of phyto.

    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 in the past without any problems.  Instead of air stones, most people recommend rigid air line tubing.  In addition, you'll need an air pump, flexible air line tubing, a gang valve, and a check valve.

     

    Aeration circulates the non-motile algae, which exposes the individual cells to the light and helps prevent them from settling to the bottom.  Remember to shake the culture(s) at least twice a week. I have an extra cap for my bottles, in order to shake them up without spilling; but you could just put your finger over the hole instead.

    Temperature

    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.

    Lighting

    I originally used compact florescent work lights, but I had one melt down and nearly cause 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 the smaller top (which is also partially blocked by the cap).

    Harvesting Phyto

    072318c.jpg.gif

    You must regularly harvest your culture to keep it going. I harvest half of it weekly by doing the following:

     

    • [Optional] To remove any larger particles, you could strain the culture through a 53 micron plankton sieve (available at Amazon).  Nannochloropsis is only about 4 to 6 microns in diameter.[1]
    • Harvest/remove half the culture (1 gallon in my case).  This is what you will use to continue your culture.
    • Make enough saltwater to double your culture, and let the salt mix dissolve thoroughly.
    • Mix the harvested phyto into the new saltwater; and add 1.5ml of f/2 fertilizer per liter (6ml per gallon in my case) into the newly diluted phyto.
    • 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 sanitize the bottle (just make sure you thoroughly rinse and dechlorinate it afterwards).
    • With the help of a funnel, pour the new culture back into the clean culture bottle(s).
    • The remaining phyto is yours to do with as you wish (like dose your tank and/or provide phyto for a rotifer culture).

     

    Foaming on top of the culture usually indicates that harvesting is overdue.  However, I usually judge harvest time by the color of the culture (it should be a dark green).  I harvest my cultures about once a week.  About half of my harvested phyto culture goes to keep my rotifer culture alive, the rest is used to dose my tanks.  If using more than one culture bottle, you could potentially harvest them on different days.

     

    When just starting a culture, it will be fairly pale in color.  Let it green up a little before you start harvesting it.  However, you should still continue to add f/2 weekly (and give them a gentle shake).  You'd be surprised just how small of a sample is required to start a culture.

    Storage

    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 somebody else doesn't mistake them for something else.  You can keep phyto in the refrigerator for up to a month; although fresh phyto provides the best nutrition.

    Dosing Phytoplankton

    Gently shake or invert the refrigerated water bottle before dosing.  You can 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.  Avoid contaminating the culture with aquarium water (pour some phyto into another container if you are target feeding multiple specimens).

     

    To broadcast feed your tank, start slowly and work up from there.  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 1ml per gallon weekly and adjust from there.  It's not unusual for me to dump a pint of phyto in 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).

    Resources:

    1. Wilkerson, Joyce D.. Clownfishes. Microcosm Ltd.. Kindle Edition.
    2. https://www.liveaquaria.com/product/3249/phycopure-green-water
    3. http://floridaaquafarms.com/
    4. https://www.algagen.com/phycopure1.html

    Edited by seabass

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    Excellent write up.  Easy to read and extremely practical.

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    The inclusion of Dino, cyno and diatoms as phytoplankton shows how interconnected the algae kingdom is.

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    How often do you dose the Micro algae grow and Kent essentials?  Would the initial salt batch not include all of the essential elements?

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    I dose both when starting the culture, and each week when I harvest it.  Depending on how large of a culture you are starting with, you might have to dose weekly without harvesting any (until it darkens up).  Also, when starting a culture, you might choose to double up on the Micro Algae Grow.

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    So this is what happens when you don't shake your culture and let it go for too long.  If this happens, don't worry, your culture is still probably fine.  Shake the culture, add some more nutrients, and filter out the larger chunks.

    phyto081118a.jpg

     

    Here's the culture after shaking and straining it.

    phyto081118b.jpg

     

    Here's the culture afterwards.

    phyto081118c.jpg

     

    Don't be afraid to add more microalgae fertilizer if you feel that the culture isn't darkening properly.

     

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    I'm also going to include this link to some experiments that I performed in starting a phytoplankton culture just from sitting out a bowl of water on my screened in porch:

     

    It demonstrates how easy it is to start a culture.  It also documents how much f/2 I used to get the culture going.

     

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    Nice!! I also started my own phytoplankton cultures, I use for my tiger pods. 

    6F050970-14C3-4EA3-B83F-8DF1A415899E.jpeg

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    My university grows phytoplankton sometimes for experiments. Some of it is done in containers that are on top of machines that shake them constantly, which is a bit noisy but probably very helpful in keeping it from settling it out. Some of it just gets shaken manually, though. 

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    ECLS Reefer

    Posted

    Okay, Mr Seabass, here’s my Phyto cooking conundrum: 

     

    Im culturing 4 types of green: nannochloris, Nannochloropsis, dunaliella and tetraselmis. They grow but they don’t get super glow in the dark green like others. I’ve only used two culture discs for each, in a two(?) three(?) month span- I lose track of time these days. So I’m getting a pale ale version of everything 🤦🏽‍♀️
     

    I feed them neophos and neonitro once a week, reef trace once a week and guillards F/2 every three days. I drain some off every three days or so, and add new water about once a week. Keep the salinity at 1.015. I haven’t tested the phos or nitrate level because honestly I was kind of scared to see how high it was. 
     

    Today, after reading around more, I decided to get new containers, and split each culture in half, adding new water and more guillards to them. They’re green as I stated but pale green. So I assume that means alive, but not super actively growing. 
     

    Now bear in mind I’m growing this stuff in my garage north of Houston where it’s hot enough to be it’s own level of hell in Dante’s Inferno. So that could be one factor. I have (dont laugh) cooling fans and a small personal AC unit on the shelf to blow on the containers. But I’m not sure if I’m not feeding them right or not swapping out containers like I should or just what, to achieve a strong uber green growth. Today was the first time I got new containers- usually I just drain off some volume and add new water and guillards, trying to use the same container forever. 
     

    What do you think I could do differently to get the same growth others have?

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    @Dirté Sanchez, here's what I've been doing which may to differ the most from your method:

    • I try to harvest the culture once a week.  When I do, I dose massive amounts into my tanks, but most of it gets poured down the drain (saving maybe a bit more than a quart, out of the two gallons).  Instead of large doses once a week, I should probably put it in a bottle (stored in the refrigerator) and dose smaller amounts daily.
    • Then I make new water (2 gallons).  While it's dissolving, I clean out the bottles with a bottle brush and tap water (sometimes some vinegar if the brush can't clean it well enough).  Once the water is fully dissolved, I add the saved culture.
    • I'll add 3 to 4 ml of Micro Algae Grow f/2 per gallon of water (so 6 to 8 ml in my case), nothing else.  If your cultures aren't darkening up as you'd like, try upping the dose a little.
    • Then I pour the new mixture into the cleaned bottles (and leave them alone for a week).

    I find that this works pretty well, even if the starting culture is quite light/transparent in color.

     

    Other notes:

    • I use two one gallon bottles.  It's suggested that you harvest one at a time (alternating), but I do them at the same time.  If one looks better than the other, I save the culture from there.
    • Lately I haven't been shaking the cultures.  That doesn't seem to be causing any problems.

     

    I'm thinking that you may need to harvest a larger percent (more new water).

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    ECLS Reefer

    Posted

    18 minutes ago, seabass said:

    @Dirté Sanchez, here's what I've been doing which may to differ the most from your method:

    • I try to harvest the culture once a week.  When I do, I dose massive amounts into my tanks, but most of it gets poured down the drain (saving maybe a bit more than a quart, out of the two gallons).  Instead of large doses once a week, I should probably put it in a bottle (stored in the refrigerator) and dose smaller amounts daily.
    • Then I make new water (2 gallons).  While it's dissolving, I clean out the bottles with a bottle brush and tap water (sometimes some vinegar if the brush can't clean it well enough).  Once the water is fully dissolved, I add the saved culture.
    • I'll add 3 to 4 ml of Micro Algae Grow f/2 per gallon of water (so 6 to 8 ml in my case), nothing else.  If your cultures aren't darkening up as you'd like, try upping the dose a little.
    • Then I pour the new mixture into the cleaned bottles (and leave them alone for a week).

    I find that this works pretty well, even if the starting culture is quite light/transparent in color.

     

    Other notes:

    • I use two one gallon bottles.  It's suggested that you harvest one at a time (alternating), but I do them at the same time.  If one looks better than the other, I save the culture from there.
    • Lately I haven't been shaking the cultures.  That doesn't seem to be causing any problems.

     

    I'm thinking that you may need to harvest a larger percent (more new water).

    I forgot to add I use 4in air stones turned down low for aeration- I don’t remember why I chose that route other than maybe comfort? Each container is a gallon though the news ones are slightly larger. 
     

    I hate the thought of pouring it down the drain, but I’m afraid nobody will want my Phyto if it’s not super green like expected, even though it’s still a live culture. But we shall see. I’ll work on culling more and see if that helps and maybe rotating out the containers to keep them clean.

     

    You don’t think the heat is killing it? I guess that’s my biggest fear that maybe I shouldn’t culture it during the summer. 

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    1 hour ago, Dirté Sanchez said:

    You don’t think the heat is killing it? I guess that’s my biggest fear that maybe I shouldn’t culture it during the summer. 

    I culture indoors.  Yes, the heat could be affecting the cultures.  According to the book Clownfishes (which I recommend, even if only culturing phyto and/or rotifers):

     

    • Nannochloris oculata - Temperature (˚F): 50-97 (77-86 preferred)
    • Nannochloropsis oculata - Temperature (˚F): 50-86
    • Tetraselmis - Temperature (˚F): 45-86 (68-82 preferred)

     

     

    On a sidenote, for lighting, I'm using a standard 75W equivalent LED bulb (daylight spectrum).  I also am not using an air stone, as they are harder to keep clean than rigid air line tubing.

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    I think I want to start dosing phyto in my reef tank, to try and get my copepods to multiply. I'm trying to help them rebound from my latest incident, but it seems like it could also be good to do on a regular basis. My fish mostly eat pods, so I don't have to worry about feeding them more than a couple times a week. 

     

    I think my tank holds about 3.5 gallons of water? It's 4.5, but of course has rockwork. Any idea how much phyto I'd be dosing, if I wanted to add it roughly once weekly, to get copepods to multiply and flourish? And hopefully to maintain a few mini feather dusters, I'd like to find and add a few of those little red ones. 

     

    I'm trying to figure out if it's worth starting a culture. My LFS sells a 16-ounce bottle of mixed species phyto that says to dose 1/4oz per 10 gallons, daily or every other day. Dosed daily, that would last my tank 168 days, and it says it lasts 4-6 months if refrigerated. Rounding up a little and dosing once a week, that's an ounce a week and a 4-month supply. 

    Any idea what an ounce of phyto a week would do in a pico tank? It doesn't look super concentrated, it's not really dark green. 

    I assume there aren't any reasonable cultures that give just an ounce a week. 

     

    It's too bad phyto doesn't keep if you freeze it. Otherwise I could run a couple of big cultures for awhile and get a few years' supply. 

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    seabass

    Posted

    5 minutes ago, Tired said:

    Any idea how much phyto I'd be dosing, if I wanted to add it roughly once weekly, to get copepods to multiply and flourish? And hopefully to maintain a few mini feather dusters

    With cultured phyto, I feel that you can dose more without a negative impact.  Just speculating, I'd guess up to about a ½ cup would be alright.  Maybe work up to that. :wink:

     

    You could easily culture this much with just a typical water bottle.

     

    3 minutes ago, Tired said:

    it says it lasts 4-6 months if refrigerated

    The longer that phyto is refrigerated, the less nutritious it becomes.  Ideally, you would keep phyto refrigerated for less than a month.

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    Good to know about the shelf life, thanks. 

     

    Are there any alternatives to an airstone? Will a tiny pump of some sort also work? I've never been able to find an airstone that's silent enough for my liking, they always vibrate too much, but I've found some pretty quiet pumps. Or maybe even one of those magnetic stirrers chemistry labs have, though I'd have to see how loud those are. 

     

    I might just pop some of this bottled phyto and a small pump into a clean jar, see if that goes anywhere. 

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    seabass

    Posted

    2 minutes ago, Tired said:

    Will a tiny pump of some sort also work?

    I imagine that would work for a much larger container; maybe not so much for a water bottle.  You'd definitely want to use Nannochloropsis, which has a thicker/tougher cell wall than many other varieties.  This will hopefully help protect the culture from the small fountain pump.

     

    Or maybe you just need to find a place where the vibration sound isn't annoying.

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    Part of the problem is that I have really sensitive hearing, and this culture would be coming with me to a college dorm room. I'd have a hard time finding anywhere in there where the pump wouldn't be annoying. 

     

    I'm gonna give this a shot with a gallon jug, a small fountain pump, and some of the bottled phyto I have in the fridge. If it fails, oh well, I've lost nothing significant. 

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    Hello, I think I’ll give this a shot too.

    I will need phyto primarily to feed Copepods. My tank is a 32g. 
    I’m guessing a 2 litre glass jar would do?

    Now, is there a species that would satisfy both Copes and Roits …. or is that a stupid question. X

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    3 hours ago, Tritone said:

    I think I’ll give this a shot too.  I will need phyto primarily to feed Copepods. My tank is a 32g.  I’m guessing a 2 litre glass jar would do?

    You typically see people use plastic bottles with screw on tops (which are easy to drill a hole in).  However, just about any container will do.  You could probably use an open container, but I feel that a covered top will help keep things out while preventing most of the evaporation.  It might also do something to help heat the culture.

     

    3 hours ago, Tritone said:

    Now, is there a species that would satisfy both Copes and Roits …. or is that a stupid question.

    Definitely not a stupid question.  Nannochloropsis oculata is probably one of the easiest to culture.  However, it has a tougher cell wall than some other species, so it's harder for some of the pods to digest.  Still, I'd guess that it's likely fine for both.

     

    Another option might be spirulina powder, which is also used to culture pods.

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    4 hours ago, seabass said:

    You typically see people use plastic bottles with screw on tops (which are easy to drill a hole in).  However, just about any container will do.  You could probably use an open container, but I feel that a covered top will help keep things out while preventing most of the evaporation.  It might also do something to help heat the culture.

     

    Definitely not a stupid question.  Nannochloropsis oculata is probably one of the easiest to culture.  However, it has a tougher cell wall than some other species, so it's harder for some of the pods to digest.  Still, I'd guess that it's likely fine for both.

     

    Another option might be spirulina powder, which is also used to culture pods.

    Thank you as always. I shall look into both options at once.

     

    T

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    Kindanewtothis

    Posted

    What is the phyto/salt water ratio to start the culture? 

     

     

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    31 minutes ago, Kindanewtothis said:

    What is the phyto/salt water ratio to start the culture?

    As much as you can spare.  The more you use, the sooner you have good phyto to harvest.  But in theory, you could start a culture with just a few ml (but it'll take a month or so before it's dark green).

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    Kindanewtothis

    Posted

    What about the foaming? Isn't it when haversting is overdue?

    20210827_161546.jpg

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    Typically.  Although it might also be to much air flow.

     

    The very top pic (with the Greenwater title), shows a decent amount of flow.  I might run just a tad bit more today (but not a whole lot).

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