# Tank maintenance & water change frequency



## DKRST (Jan 11, 2011)

Is one, large, weekly change any better than two smaller? Is there any reason to cut back to one change/week or less? Maintenance routine: Water change on Wed and Saturday, about 30% of water volume each change (estimate actual water in tank @ 45-50 gallons). Dose with Flourish comprehensive on M,W,F. Daily dosing with 5ml of Excel (I don't overdose Excel w/water changes).​Tank info:55 gallon, heavily planted (amazon swords, ozelot sword, brazilian sword, queen radicans, rosette swords (a bunch), rapidly growing rotalia, cabomba, myrophillium, anubias, frogbit, water sprite, and pennywort. Inhabitants: 4 angels, two bristlenose plecos, 5 pepper corys. Filter: Eheim 2215 Light: T5HO x2 (with fiberglass screening to cut light levels). Parameters: ammonia, nitrate, nitrite all at 0. pH @6.8​I guess with my overdosing of the flourish comp, I'm (expensively) simulating EI dosing to a degree. To date, everything's working well in the tank. I kind of like my weekly "tank time". Without repeating http://www.tropicalfishkeeping.com/...r-changes-really-they-necessary-debate-64691/ all over again, I was wondering what folks thought about my water change routine? Note: I am bad about overfeeding!


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## zof (Apr 23, 2010)

I dread water changes, in fact so I usually only do it every two weeks now but then my tanks are heavily planted, lightly-moderately stocked and nitrates rarely get above 10ppm.

I can see a few issues with doing a water change greater then 50% though, one, established tanks pH typically differ from the pH coming from tap due to organic decay. Two the more water you change at one time the more likely you can temperature shock your fish if your not really close to the tank temp. Three I think its less stressful for the fish to have ample room while you change the water. Four the lower you take the water level the more likely you will brake steams off of the taller plants if floating plants get stuck on those plants.


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## kitten_penang (Mar 26, 2008)

i dose my tank every monday and thursday so every sunday i do a 20 percent water change and it works well for me


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## Beaches (May 28, 2011)

If your routine is working for you and your fish DKRST, then I wouldn't change it. What works for one person, may not work for another, finding out what does work for your tank/fish is the important thing and then I would stick to it.

I prefer to do smaller water changes.....you can always do more if need be. I agree with zof's comments, plus any major fluctuations caused by large water changes may also affect/hinder the nitrifying bacteria.


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## AbbeysDad (Mar 28, 2011)

DKRST, this is an interesting puzzler my friend! 

If we look at fresh water in nature we would conclude that some areas receive almost daily rainfall (e.g. the rain forest) while other areas receive a little rain now and again and/or the torrential rain fall. We might also note that rainfall varies at different times of the year.

In the case of our tanks, with the purpose of diluting dissolved yuk, I'm not sure it matters as long as we do it often enough, in quantities sufficient to 'freshen' the water by diluting the existing water. We might say that a 25% biweekly change is nearly (but not exactly) the same as 50% weekly.

Now as to the amount, there is something to be said for the tank water condition as compared to the tap. If one adjusts for pH or has wood or other elements that alter pH, there may perhaps be an associated negative relative to the quantity of the water change. I have not seen any negative effects doing 30%-50% water changes (but I do not adjust for pH or have anything that acidifies the water).

So, bottom line, I think your method is fine, but probably not significantly different to doing a somewhat larger water change weekly. I have been doing a nearly (but not quite) 50% water change weekly and it seems to be working fine.


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## kitten_penang (Mar 26, 2008)

i like using ro when i do water change it does wonders to dilute the gunk lol


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## DKRST (Jan 11, 2011)

One thing I should have mentioned. My tapwater comes out at 7.0, and it's soft. My tanks are all within just a couple of tenths of pH 7, so the potential pH "shock" it's not an issue. For me, I'm more worried about stress of pH change from water replacement as my tanks drift lower over time (due to tank wood) so that is one reason I prefer more frequent water changes. Temps not an issue, I make certain the temp matches before it goes in the tank (I'm an old fashion bucket-dumping kind of guy!).


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## Mikaila31 (Dec 18, 2008)

I do 50-60% weekly on most my tanks. I'm honestly not worried about pH changes or temp changes. I don't bother with matching the temps exactly. Sometimes I will do cold water changes if the tank is hot, enough to drop the tank temp 4 degrees or more. Any healthy fish should not have a problem with these changes.


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## DKRST (Jan 11, 2011)

Mikaila31 said:


> I do 50-60% weekly on most my tanks. I'm honestly not worried about pH changes or temp changes. I don't bother with matching the temps exactly. Sometimes I will do cold water changes if the tank is hot, enough to drop the tank temp 4 degrees or more. Any healthy fish should not have a problem with these changes.


Do you do a single change weekly? If I remember, you dose dry ferts?
I don't generally do a 4 degree temp difference, but I often estimate the water temp by the (error-prone) finger-dip comparison. I have verified the temps and I'm usually within 1.5 degrees +/- using just the finger-check method.


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## Byron (Mar 7, 2009)

I'll add some math to the issue. With respect to just the volume of water changed, the more you change the more "crud" will be removed. Crud refers to dissolved (liquefied) fish waste, urine, pheromones, etc. Crud cannot be "removed" by filters [except to some extent live plants] so only a water change will remove this pollution--and pollution is exactly what it is. In natural waters it would be removed rapidly by water movement in streams, thermal currents in lakes, rainfall and evaporation, etc. A water change is essential to remove it from a closed system aquarium.

Crud is constantly being added to the water by the fish. The less water that is removed and the less often, the more crud builds up. So mathematically it is better to remove more water and more often.

The value of larger weekly water changes over smaller twice weekly changes is in the level of pollution that remains after each. The fish will be exposed to less pollution for part of the week if a larger water change is performed, as opposed to changing less water more often which leaves more pollution in the tank throughout the week.

The biology of the tank should determine the frequency and volume of water changes. The fewer fish and more plants and in a larger volume, the better the biology should be--theoretically at least. This is why some natural planted tank aquarists can advocate a water change once every six months, or less; but they are quick to point out that this works in tanks thick with plants and a modest fish stocking. The more fish in a given volume of water, the more essential are larger water changes and more often.

You can raise 30 discus fry in a 40g tank by doing 95% water changes several times each day. The fish will grow fast and be very healthy. The same fish in the same tank without the water changes will be poorly developed and stunted, if they even live through it. Clearly it is not the tank size here, but the water changes. And there is enough evidence that this is not a matter of nitrification alone, but the "crud" that we can't see and can't measure with test kits.

Allowing a drop in pH or a rise in nitrates to dictate water changes is very unsound. By that point it is too late; the damage to the fish has occurred. Health problems down the road, including a premature death, can be traced back directly to poor maintenance.


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## DKRST (Jan 11, 2011)

Byron said:


> The value of larger weekly water changes over smaller twice weekly changes is in the level of pollution that remains after each. The fish will be exposed to less pollution for part of the week if a larger water change is performed, as opposed to changing less water more often which leaves more pollution in the tank throughout the week.


Thanks Byron - great information as always! Your expertise is appreciated.


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## MetalArm3 (Jun 22, 2011)

I've noticed if I do large water changes (anything above 50%) my tank usually has a bacterial bloom that last a few days. It isn't harmful to the fish at all but it's not very appealing.


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## Byron (Mar 7, 2009)

MetalArm3 said:


> I've noticed if I do large water changes (anything above 50%) my tank usually has a bacterial bloom that last a few days. It isn't harmful to the fish at all but it's not very appealing.


This was mentioned in another thread [not sure who by, could have been you] and I indicated that I have some cloudiness with each water change. I change 50-60% in all my tanks. The ones with sponge filters clear within an hour. The larger tanks with canisters usualy are clear overnight, and one sometimes longer. I am not sure this is a bacterial bloom, though it might be.

My initial thinking is that it is simply miniscule particulate matter suspended in the water column, either from the tank itself or in the tap water. [Have a good look at a glass of tap water, mine is not always crystal clear.] But it could also be a bacterial bloom; the organics in the tap water would suddenly provide food for heterotrophic bacteria which can multiply within 30 minutes in de-chlorinated water, hence the bloom. In either case, it is not harmful to fish.


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## MetalArm3 (Jun 22, 2011)

I thought it was bacteria because mine remains in the tank for several days if not a week. But thats if I only do huge water change (like my last 75% to remove medication). Could miniscule particles remain suspended that long, it seems unlikely? A fascinating observation. I live in Credtwood IL and it's said they used contaminated water mixed with Lake Michigan water to provide to us residents. So who the he'll knows what's in our taps at times!

Interesting reading: Fact Sheet - Crestwood Public Drinking Water Supply Contamination, Crestwood, Illinois


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## DKRST (Jan 11, 2011)

Ok, the water change frequency make perfect sense, thanks to Byron. Geez, you'd think with a PhD I wouldn't need the obvious pointed out. That's why my degree's not in math 
Here is the frequency vs. volume issue recapped for those math challenged like me:
_
For example :_ 
If I had a 200 gallon tank, and I changed 50 gallons twice a week (a 25% x 2 change).
Monday water change: I remove 50 gallons of water (25% of tank water, 25% of pollutants). 
Thursday water change: I remove 50 gallons of water BUT...
Part of that water is the "oldest" water and part is the "new" water from Monday's change.
Statistically, it is 6.25% (12.5 gallons) of the "Monday" water and 18.7% (37.5 gallons) of the oldest water. This means instead of getting a clean 50 gallons, you only really refreshed 37.5 gallons on Thursday. 

Interesting….



MetalArm3 said:


> I've noticed if I do large water changes (anything above 50%) my tank usually has a bacterial bloom that last a few days. It isn't harmful to the fish at all but it's not very appealing.


I had a similar problem when doing a medication treatment. No bacterial bloom, but I had a diatom outbreak. Plants were brown for two weeks, but my new bristlenose were really happy!

That's the next question regarding water changes. *Less frequently may be better from an absolute water refreshing standpoint, but how much is too much at each change or, as I suspect, is the max change volume dependent on a tank's particular situation?*


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## zof (Apr 23, 2010)

DKRST said:


> *Less frequently may be better from an absolute water refreshing standpoint, **but how much is too much at each change or, as I suspect, is the max change volume dependent on a tank's particular situation?*


I think your right on there, ever tank and situation is different, a heavily over stocked tank would benefit (if not be necessary) to do bi-weekly water changes at the "max" amount. But on a normal or light stocked tank would be fine with the weekly max water change. As for the max everyone is going to have a different opinion 50% seems reasonable to me unless you are trying to remove medication or treat some disease.

We want the cleanest environment possible for health and well being of our fish but at what point does this become overkill, I could setup my tanks to run a 100% water change every day (at least by putting in and taking out that much water which in the end by math would be closer to a 50% water change with a drip system) but at which point does it no longer strongly benefit the fish and just becomes a waste of water.

Every stocking situation is different and this is where the test kits come in to measure for the pollutants in the tank so we can gauge how much and how often we need to change the water.


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## Byron (Mar 7, 2009)

I'm sorry but I must disagree with using bad test results as the criteria for a water change. By that point it is too late in a sense, because the bad conditions have taken some toll on the fish. I'll expand a bit on this before I turn to the volume issue.

Taking nitrate for instance. If nitrate is normally 10ppm, and you test once a week, and one week it is 15ppm or 20ppm, the increase in nitrates has likely affected the fish. Some species are more sensitive to nitrates than others. As I mention in my article on bacteria, high levels of nitrate, above 40 ppm, have been shown to slow fish growth, suppress breeding, and depress the immune system making the fish much more susceptible to disease. Considering that all our fish occur in natural waters with near-zero nitrates--and I could cite test numbers for several Amazonian and SE Asian streams showing nitrate so low it is unmeasurable--an increase of 5 or 10ppm is significant. The whole aim of regular maintenance including partial water changes is to maintain stability and prevent any fluctuation. That is more likely to lead to better fish health.

And stability brings me to the volume issue. Obviously the replacement water should be close to the tank water in many respects. Hardness, pH and temperature are obvious, but there are many others, including bacteria, organics, nutrients. And as Mikaila correctly noted, some variation is not bad, in fact the opposite; there is no need to "prepare" identical water with respect to these parameters, but the variation should not be astronomical either. My tanks run at pH 5 to 6.4 depending upon the tank, and one is 7.2 for basic water fish. My tap is 7.0, so changing 60% of the tank means replacing pH 5 water with pH 7. Yet I have never had any indication of a problem, and largely due to the biological stability which "buffers" such changes so they are less; the tank pH rises maybe .3 or .4, that's it. And I almost always use cooler water, using the hand test someone mentioned earlier. And all of this is also perfectly natural; fish in Amazonia spawn when the water temperature drops significantly (several degrees) and there is a corresponding change in pH, as studies by Stanley Weitzman and others have proven.

It is a false assumption to assume that doing smaller volume changes will somehow create more stability. Chances are, it will be the exact opposite. If the conditions are allowed to deteriorate to the extent that our flimsy test kits actually register them, things are probably much worse in actual fact. Suddenly changing such water can sometimes cause other problems like ammonia poisoning, nitrite poisoning, pH shock, etc. The fact is that water which is changed more regularly in significant amounts will be more stable. The tank's biological balance will be determined by the fish, plants, additives, organics, and water changes. Maintaining a schedule of higher-volume and weekly changes ensures this true stability will more likely hold. There will be much less of a "pull" biologically if the water is replaced more often and/or in greater quantity. Refer back to my comment on the discus fry previously.

Those of us who change 50-60% weekly and have done so for 20+ years know there are benefits to the fish. My fish are always more active, colourful, more likely to spawn, and "playful" the day following a water change. But my water parameters do not ever fluctuate from week to week, so while testing pH, nitrate, ammonia, nitrite, CO2, whatever would show absolutely no variance, the water change clearly has done something. And it comes back to that "crud" I wrote about previously, that cannot be measured in any way, but is certainly present if there is a live fish in the tank. That crud is what we are removing and replacing, and it is essential to do so--if you want healthy fish.


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## AbbeysDad (Mar 28, 2011)

Is 'crud' a TF tech term? 

I agree that there are all sorts of no-see-ums that lower water quality that test kits can't show us. 
In addition to our N2 bacteria, there are decomposition bacteria that reduce waste into more harmless humus like compounds, but in the process, there are acids, gases, some organic compounds, etc. released along with other waste elements and pheromones....AND nitrates = only through water changes do these get reduced.

Now, I will agree that the WWC is a bit of a pain. Wouldn't it be neat to have a tank with an overflow and add a slight constant flow (more than a drip, less than a stream) of fresh, temperature controlled water...so that fresh water was constantly flushing the tank. (Oops, I forgot for a minute about you folks with chlorinated water supply - that complicates things further.) Well, just a thought


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## Mikaila31 (Dec 18, 2008)

Gasses gas out of the water though and live plants uptake A LOT of the elements that build up in an aquarium. Most stem plants and as well as floating plants take most of their nutrients from the water column. As far as acids go it depends on your buffering capacity and the types of acids.


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## DKRST (Jan 11, 2011)

*Model of pollutant load vs water change patterns*



Byron said:


> ... using bad test results as the criteria for a water change. By that point it is too late in a sense, because the bad conditions have taken some toll on the fish.


 I agree totally. Been there, killed those fish.


AbbeysDad said:


> Wouldn't it be neat to have a tank with an overflow and add a slight constant flow (more than a drip, less than a stream) of fresh, temperature controlled water...so that fresh water was constantly flushing the tank. (Oops, I forgot for a minute about you folks with chlorinated water supply - that complicates things further.)


It's a viable concept. With a slow enough inflow, an inflow sump/mixing area, an overflow drain, and unchlorinated or chlorinated (not chloramine) water, it would work. Slow enough flow, and the temp's not an issue either. Trick is to use an inflow float valve and a precision valve to limit inflow rate regardless of float valve. Outflow is by overflow. No problem mechanically.


Mikaila31 said:


> Gasses gas out of the water though and live plants uptake A LOT of the elements that build up in an aquarium. Most stem plants and as well as floating plants take most of their nutrients from the water column. As far as acids go it depends on your buffering capacity and the types of acids.


Concur. Volatile components take care of themselves, non-volatiles have to be metabolized or manually removed.

I'm playing around with a spreadsheet to show exactly how much old water/pollutants are removed using various water change patterns. 
Fact: the math (thanks Byron ) shows that multiple small water changes can remove the same total amount of "pollutant units" per week as one large one. However you have to physically change _more _gallons of water with multiple smaller changes than with the one big weekly change to get equivalent results. There is the issue of average pollutant levels with each routine. I'm working up a simple model to look at the average daily "pollutant level" under each water change routine. I'll post an update when I get around to finishing and I'll post a link to the file for folks to double check my results! Should be an interesting graph, but I anticipate no major revelations...


Right now, I've got to finish grading some papers from summer semester...


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## AbbeysDad (Mar 28, 2011)

DKRST,

In round numbers, I think we'd need to do bi-weekly 35~% water changes to approximately equal the 50% weekly change in terms of 'crud removal/dilution'. (note: that's just off the top as I didn't bother to make my head hurt with relational equations as I'm not sure we really need to be so precise) 

I also think the water change requirements are based on the specifics of the tank. The bio-load, living plants and to a degree filtration - even a bubble wand can make a difference in releasing unwanted gases.
Maintaining water quality is multi-dimensional and we can only speak in general terms.
(e.g. the over stocked tank might be maintained with more frequent/larger water changes, while the under stocked tank can be maintained with less). To say that all tanks would be fine with x% weekly or y% bi-weekly water changes would not necessarily best serve all circumstances.


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## Byron (Mar 7, 2009)

AbbeysDad, "crud' is the term coined by David Boruchowitz in a two-part article on this very issue of water changes. He uses "crud" to cover all the stuff we can't detect but fish produce, and which can *only* be removed by changing water.

And DKRST, that article did what you are propsing exactly; David worked out the mathematics and science on the effects of daily versus weekly water changes, and using amounts from 10% to 70%. It is in the November and December 2009 issues of _Tropical Fish Hobbyist_ if you want to see it. If you have a subscription to TFH you can see this online (their magazine is now online as well as in paper, back to about 2006 I think). But I happened to have scanned these for someone, so I can send them to you if you PM me with your personal email [can't have attachments to PM's on the forum, so has to be your own email].

Byron.


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## zof (Apr 23, 2010)

Byron said:


> I'm sorry but I must disagree with using bad test results as the criteria for a water change. By that point it is too late in a sense, because the bad conditions have taken some toll on the fish.


While I agree that if you let nitrates get to 30 or 40 ppm to signal a water change you have already failed, its important we know how much and how fast waste is building up in the aquarium. While 50-70% water change might be a good catch all for a water change many times with a light stocking in the aquarium a 20-30% water change will accomplish the same as the 50% in a fully stocked tank. Sure the fish wouldn't mind the extra fresh water but do we really need to waste that much extra water for lighter stocking on the tank (unless of course you drain the water into a garden in which switching the extra water you would put in the garden with the tank water would make perfect sense). The testing we do is a tool to help gauge these things and should only be used to help estimate what is right for your aquarium but is not a trigger for those things.


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## DKRST (Jan 11, 2011)

*Big & frequent water changes are best*



Byron said:


> And DKRST, that article did what you are propsing exactly; David worked out the mathematics and science on the effects of daily versus weekly water changes, and using amounts from 10% to 70%. It is in the November and December 2009 issues of _Tropical Fish Hobbyist_ if you want to see it.
> Byron.


The response title on this post says it all, and it's kind of a "duh" thing. Wow - cleaner water is better for our fish, who would have ever thought that :lol:

Ok Byron, I am _thoroughly convinced_! An excellent article with sound logic and the math to back up all the assertions. The math is simple and doesn't lie. I'm going to do much larger water changes than I currently perform, but that also allows me to do them a little less frequently and keep a lower average level of pollutants in the tank. I'll probably stick with two changes of around 50-60% a week in my smaller non-planted tanks and go with one large, 60-70%, in my planted 55. That will allow me to use a modified EI nutrient dosing in my 55 much more safely (won't have to worry about build up of nutrients).

Thanks again Byron, I learn more from your daily posts than I'd learn in 5 years on my own.


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## Byron (Mar 7, 2009)

zof said:


> While I agree that if you let nitrates get to 30 or 40 ppm to signal a water change you have already failed, its important we know how much and how fast waste is building up in the aquarium. While 50-70% water change might be a good catch all for a water change many times with a light stocking in the aquarium a 20-30% water change will accomplish the same as the 50% in a fully stocked tank. Sure the fish wouldn't mind the extra fresh water but do we really need to waste that much extra water for lighter stocking on the tank (unless of course you drain the water into a garden in which switching the extra water you would put in the garden with the tank water would make perfect sense). The testing we do is a tool to help gauge these things and should only be used to help estimate what is right for your aquarium but is not a trigger for those things.


I think we're really talking of two different things. First, there is the stuff that causes nitrates to rise (if unchecked), namely the visible "waste" from fish that become organics and should be handled by the bacteria and live plants. Second, there is the "crud" that you simply cannot measure, but we know it is there because there are fish.

Both are in proportion to the fish load, true, but they are not necessarily related. As an example, in my tanks with all my plants, the "waste" is easily being handled. I see nitrates < 5ppm and have for years. It doesn't matter how many fish, relatively speaking; the nitrates are minimal because of the plants, snails and bacteria. So if I took nitrates as an indicator of a water change, I would never do one, and my weekly water changes are really not impacting "waste" at all because I never remove it from the substrate. Of course, if I never did a water change, the nitrates might rise. But with all my plants, I'm not sure this might not take a while, by which time the "crud" issue would be out of control. And given the number of fish I have in my tanks, the "crud" is the real issue and it is completely undetectable, or at least until it is too late when the fish's response would alert me if I let it go that far.

The fact that my fish respond so enthusiastically to a water change when all the test parameters remain excellent is proof of this as far as I'm concerned. The invisible and undetectable "crud" is getting removed by 50% every week, and this has a significant impact on fish health.

It is true that with few fish the "crud" would be less too. Those planted tank folks advocating no water changes are quick to point out that it works if the fish load is "moderate" and the plants are heavy. I recall reading one author who said the "no water change" works fine provided the fish are "balanced" and the example he used was 6-7 neon tetra in a 55g tank. The plants could handle everything at this level of balance. Most of us keep more than half a dozen small fish in a 55g tank.

Byron.


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## HMlairy (Jan 22, 2011)

I do a bi-weekly 30% water change/gravel vacuum. That keeps the nitrates away generally


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