New water change schedual

[fish n' pets]

You know how everybody says that weekly water changes are essential? Well, i have been doing them, but it puts lots of stess on me with school and everything else going on in my life. Now that school is over (this year, anyway!), i want to figure out a better way to manage my time. I thought it would be easy if i could do daily water changes. Like, two cups a day then 4 cups one day a week. That would equal 16 cups, or 1 gallon. It would be as quick and automatic as feeding the fish or dogs! I just wanted to know if i started to do that, would i have to continue topping off? I don't top off much anyway, about once every 2-3 days. It would keep the tank really stable, and it would be easier for me! Tell me what you guys think.

[Gill Snork]

Its a nice sounding schedule, but it wouldn't work. I threw together an excel spreadsheet so I don't have do the math and so I can graph the results:

 

Since you are doing the water changes throughout the week when nitrates are low compared to the end of the week (when they have accumulated to higher levels) , you do not remove as much from your water:

(I used metric because the math is easier):

 

1/8th liter water change for 6 days and a 1/2L water change on the 7th day(assuming a 10 gallon tank and a 1 mg/L (= 1ppm) accumulation rate per day), you would have 0.68mg/L at the beginning of the 2nd week.

 

Using the standard 20% per week using the same assumptions, you would have 0.58 mg/L.

 

Take this out to seven weeks, and you have 36 mg/L= ppm on the beginning of the 8th week for your method and 22.9 mg/L=ppm for the 20% method.

 

Additionally, the 20% method begins to level off to an almost constant nitrate range (around 26-32 mg/L- along the lines with most people's weekly readings) while your method takes twice as long to stabilize at twice the level (at 12 weeks it was still rising and was around 54 mg/L

 

Hope this helps

 

Gill

 

here is the graph:

 

 

 

[beezerv]

Great analysis Gill.

[fish n' pets]

OK, Gill, i think i understand what your saying. The graph helps. Well, it sounded nice when i thought of it...oh, well.

[clifford513]

Really precise and useful data Gill! I suck at math

[Nuhtty]

Gill, your analysis goes on the assumption of a constant rate of nitrate production in the system.

 

Nitrate production changes with feeding, defecation, temperature, skimmer cleaning and other methods of filtration.

 

I dont think you can simplify it as you did although I applaud you for your work.

 

Another way to look at it is a daily water change can potentially lessen the overall nitrogen load thereby resulting in less nitrate production by weeks end.

 

Nitrate production in a tank is not constant as you assume with your math, but rather it is exponential as toxins build up in the body.

 

A good analogy would be kidney dialysis (I think of everything in terms of medicine).

 

A patient who has kidney dialysis one time per week would be in serious trouble...thats why we do it at least 3 times per week.

 

On day one X amount of toxins build up in the system, day 2 is no simply 2 times X but rather an exponential increase based on nutrient import into the system and export by the afore mentioned filtration methods.

 

So a daily water change could break this cycle by keeping the toxin buildup from increasing exponentially.

 

What I am getting at it, give it a try! I think it would work. Although a few cups would be like peeing in the ocean unless you have a small tank.

[fish n' pets]

That's a good point, Nuhtty. I also read a book, and remembered saying that some people do daily water changes even in 100 gallon tanks! (of course, they would be slightly bigger than the schedual im proposing for my 12 g nanocube!). Besides, i don't have a very big bioload at the moment. Maybe i'll give it a try, and see how it goes. I don't get your medical anology, but maybe thats just me.

[NanoDog]

I'm not sure the dialysis is a good analogy...

 

especially in this case where the volume of the water change is different.. and doesn't go for a baseline value.. but is just less....

 

Don't you do dialysis to a certain level before stopping?...(not rhetorical.. I have no idea)

 

There's a great conversation at RC (well several) about water change frequency.. but I can't get their search to work right now... Their chem guy might have written it..

[Nuhtty]

I'm not sure the dialysis is a good analogy...

 

especially in this case where the volume of the water change is different.. and doesn't go for a baseline value.. but is just less....

 

Don't you do dialysis to a certain level before stopping?...(not rhetorical.. I have no idea)

 

There's a great conversation at RC (well several) about water change frequency.. but I can't get their search to work right now... Their chem guy might have written it..

 

My analogy with the dialysis was to simply show that overtime toxins build up and that buildup isnt a linear, but rather an exponential curve. I agree that its not the same.

[seabass]

Everyone has some good points.

 

Look at it this way. If you have a system with nitrates at 10ppm, a single 20% water change will reduce nitrates to 8ppm; however with two consecutive 10% water changes, the first water change will reduce nitrates to 9ppm and the second to just 8.1ppm (versus 8.0).

 

But you can get an equivalent reduction by increasing the total amount of water changed. So in this example, I could get a result that is similar to a 20% water change with two consecutive 11% water changes. So just change more water in total (for the week) than you currently do.

 

As for eliminating your top offs; it is easier to maintain proper salinity by topping off before doing your water change. However, in theory, they could be combined by doing a water change with lower salinity. You would just have to be more careful.

[Gill Snork]

Nuhtty,

 

I agree with your statement about the rate of accumulation, but since I do not have any data to construct a formula for nitrate as a function of time for a general system (and everyone's system would differ, as you imply with references to the various parameters that affect nitrate production), I made some simple assumptions that in the end, shouldn't be that far off from an actual system.

 

If you have any data (or if someone would be willing to track their nitrates accurately over the course of a week or two, I would be very willing to determine an approximate nitrate accumulation rate (exponentional or otherwise) by regression and plug it into my spreadsheet in place of my simple assumption. I am sure that some accurate data showing that daily water changes would be better or worse would be desireable to alot of people on here and from the data, I may be able to find a "maximum nitrate removal efficiency" aka the best water change interval.

 

I based my assumption on how most people maintain their tanks (with 20% water changes weekly), and used the stabilization values of that schedule to back calculate a reasonable accumulation rate that would reflect a normal water parameter range for nitrate.

 

If everyone on this thread were willing to track their nitrate levels for two weeks, tht would give a pretty decent data set for coming up with some really neat findings.

 

Gill

[fish n' pets]

Umm....am i the only one who's REALLY confused?

[seabass]

Umm....am i the only one who's REALLY confused?

For discussion purposes it is helpful to disregard nitrate production and consumption, which have too many variables to discuss properly (especially when your system has the ability to react to higher concentrations and increase consumption via algae growth). So putting that aside, you can substitute multiple smaller water changes for one larger water change (you just have to change a little more water for it to be comparable).

 

So for your 12 gallon cube, with a single 15% water change, you would be changing out 1.8 gallons a week. However, if you do daily water changes, you need to change out 0.276 gallons a day for the same effect. That’s 4.416 cups or 1.104 quarts a day (totaling 1.932 gallons a week versus 1.8 gallons). It’s really not that big of a difference; it’s just something to be aware of.

[BlueOyster]

Hi there, not been reefing long, i agree all of you have good points and i would tend to lean towards the idea that smaller more frequent changes would be 'better' for the stability of the tank, but would you be able to take as much fish crap and detritus etc out of the tank with 2 or 3 cups as you would siphoning into a bucket? i do a change about every 5 or 6 days and use a siphon and a bucket a good way to get the floating bits out as well. just my 2 cents

[Carlo Gambino]

I have to add a 3rd point of view.

 

This is something that I began to due about 2 months ago. Let me know your opinions.

 

As it has been agreed by everybody in this thread so far, there are many variables that go into nitrate production. Load, feeding, skimming, cheato, ect.

 

I have began to not follow a stringent water change schedule. Instead I have began testing for Nitrates every saturday and depending on my readings, I then decide when to do a water change and how much water to due.

 

Two weeks ago my reading was about ~5. I decided not to due a water change. I then tested the water last week and my reading was ~5-15 and decieded to due a 20% bringing my reading to about about ~5 again.

 

There has been times that I have had to due up to a 30% water change because my readings have gone up to ~20 and there has been weeks that I do not due a change or a small 5% water change.

 

Now on weeks that I due not due a water change, I do dose for Trace Elements, Calcium, and other suplements to replenish what has been used up.

 

I find this to be a gread method and has kept my tank more stable than before. Nitrate acumilation is at an exponention rate overall but does have spikes and valleys over a weekly time table. Now like I stated I began doing this about 2 1/2 months ago so it still is not sure the overall outcome, but if anybody cares I will let you know the results.

[geekreef_05]

My two cents: What you suggest is extra stress on the animals. Your moving from a nitrate rich environment to a low nitrate environment in a quick water change. The essense to reef keeping is stabilitiy. Not to mention, we've been focusing on nitrates here to determine when we should change the water. If I used that method in my reef, Id never change the water. Running a system like mine (fishless/skimmerless) my waste production is very tiny.

 

This being said, we should be changing water based on the aquarium's usage of trace elements, and not exclusively nitrates. What Im saying is that nitrates readings should not be the deciding factor as to whether or not your gonna do a water change.

 

Currently I have three tanks running. My 60 gallon FOLWR tank gets a 30% water change every 6 months. Because it's stocked very low and has no sensitive animals (excluding cleanup crew); this method works so far. My 15H reef gets a 30% WC every two weeks. Although there are no fish in this tank the SPS coral demands it. The water from the 15H goes into my 33L which is moderately stocked with a BTA and various softies; along with 5 fish. The FOLWR tank consistently runs at about ~5 ppm nitrates, while the other two tanks have flawless test results.

 

So, Im just saying that WC scheduals are also very dependant on the type of reef your maintaining. My advice is to experiment a little, but understand how the reef system works and remember that your water contains ALOT of good and bad *things* that we dont test for at all.

[Gill Snork]

This is turning out to be a really well rounded discussion. I'm glad its not just people saying "20% is the only way, period".

 

As another side to the coin, what about the people that do their water changes rarely if at all? I have read more than a few people on here who have not changed their water in 6 months or more and still have great sucess with a variety of stocking levels.

 

Could simply dosing with "trace elements" be sufficient if nitrate levels are consistently low?

 

I would love to see the results of your study though, as well as others with different setups. I will start tracking my tank once it gets done cycling.

 

Gill

[fish n' pets]

So, geekreef, your saying whos schedual is extra stress? I imagine mine would be even less stressful because less water is being changed, there is less of jumping around of levels. I might try the daily water changes and see how it goes.

[Bonebrake]

I feel that daily water changes would be just as successful as weekly 10% or 20% water changes and without a doubt less stress on the system.

 

I also feel that in a system that is under stocked or appropriately stocked, that with a refugium and skimmer and auto top-off, you could likely get away with never doing a water change so long as you harvested chaeto and dosed the appropriate trace elements and calcium.

 

In both situations, daily water changes and no water changes, there would be very little stress, if any, on the system because change would be so gradual.

 

The problem with the no water change scenario is that without a very expensive chemical lab and a Ph.D. in chemistry, you will not be able to monitor your trace element consumption and replace them in the proper ratio that they are consumed. There are over 70 different trace elements and they are consumed at different rates and need to be maintained at different concentrations, therefore, water changes are really the only effective way to keep them at the correct concentrations.

 

Will the no water change systems dosed with trace elements and other additives eventually crash? Who knows? Some people who are dose happy and just love adding stuff to their tank have trace element levels 100x higher than what they need to be, but everything is still alive. I would assume you could probably get away with the no water change scenario (in a large tank) and not see any consequence in your life time.

[Carlo Gambino]

The problem with the no water change scenario is that without a very expensive chemical lab and a Ph.D. in chemistry, you will not be able to monitor your trace element consumption and replace them in the proper ratio that they are consumed. There are over 70 different trace elements and they are consumed at different rates and need to be maintained at different concentrations, therefore, water changes are really the only effective way to keep them at the correct concentrations.

 

 

Bravo.... this is so true and sums up the biggest "X Factor", (if you want to put it this way) that we have in reefing.

 

This has turned out to be a very informative thread.

[clifford513]

If you keep shrimp or anemones, nitrate levels should be monitored pretty closely. Just something to think about for those lax on water changes.

[Nuhtty]

I would assume you could probably get away with the no water change scenario (in a large tank) and not see any consequence in your life time.

 

I only did one water change on my 65g in 6 months. With this tank..smaller and more expensive livestock...I am sticking to a monthly 50% change.

[geekreef_05]

So, geekreef, your saying whos schedual is extra stress? I imagine mine would be even less stressful because less water is being changed, there is less of jumping around of levels. I might try the daily water changes and see how it goes.

 

 

Although your method is no doubt the least stressful between the mentioned WC scienario's, it is likely not to provide enough nutrient export. Consider Gill's diagram of nitrate export in the reef*; the method of changing more water at once reduces nitrates much faster than changing the same amount of water over the course of time. Consider that we can basically replace 'nitrates' with most other 'bad' elements in found in reef water and see the same general pattern between the two methods. Thus if you want to efficiently change water, it is better to do it at one time.

 

However, that is not at all to say that your concept will not work. Its quite possible that for your intended bioload this is the perfect solution. Personally, my only deterent would be that fact that its gonna be a slightly maintaince heavy tank (doing mini WC's daily), but thats always a personal decision. I think that you have a great idea, and its definately worth exploration. I say, give it a try, and see where that takes you.

 

G/L,

happy reefin'

 

*I am aware that build up of 'material' in tank water will grow exponentially as well as in speratic bursts. Despite this, Gill's diagram relay's a generally correct comparision of nitrate export though water change scenario's.

[icenine]

I change as much water as I can every week.... (at least 15 gal in a 24 gal AP) ...I leave almost every coral exposed and my three fish gasping in pools just above the sand for a few moments.

 

Don't mistake aclimation to ever increasing pollution for "stable".

The more clean water the better..... in a nano there is really no reason not to.

[jerryz]

Being a newbie in salt, 2 months now. The guys at the salt LFS tried to "emphasize"/ discourage me about how rigorous this hobby (salt) was. Especialy after I told them I wanted to do a nano tank. They told me I would have to do WEEKLY water changes.

 

Now, I have spent years keeping and raising Discus. So this "rigorous" schedule alsmost made me laugh. I fyou were to tell a discus breeder that he could maintain decent water parameter with weekly water changes he would think you are brain dead. So along with daily water changes in my discus tanks I now do a weekly change in my new 20L reef tank (ouch) that such hard work.

 

THere is almost no way that daily partial changes would be inferior other methods as long as the amount was large enough to actually have meaning. In other words at least 5-10%