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Tank maintenance & water change frequency

This is a discussion on Tank maintenance & water change frequency within the Beginner Freshwater Aquarium forums, part of the Freshwater Fish and Aquariums category; --> Originally Posted by Byron The value of larger weekly water changes over smaller twice weekly changes is in the level of pollution that remains ...

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Tank maintenance & water change frequency
Old 07-28-2011, 12:58 PM   #11
 
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Quote:
Originally Posted by Byron View Post
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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Old 07-28-2011, 01:44 PM   #12
 
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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Old 07-28-2011, 03:36 PM   #13
 
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Originally Posted by MetalArm3 View Post
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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Old 07-28-2011, 04:01 PM   #14
 
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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Old 07-28-2011, 04:25 PM   #15
 
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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….


Quote:
Originally Posted by MetalArm3 View Post
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?

Last edited by DKRST; 07-28-2011 at 04:27 PM..
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Old 07-28-2011, 06:24 PM   #16
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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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Old 07-28-2011, 08:16 PM   #17
 
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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.

Last edited by Byron; 07-28-2011 at 08:25 PM..
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Old 07-28-2011, 08:40 PM   #18
 
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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Old 07-29-2011, 02:39 AM   #19
 
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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Old 07-29-2011, 07:35 AM   #20
 
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Model of pollutant load vs water change patterns

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Originally Posted by Byron View Post
... 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.
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Originally Posted by AbbeysDad View Post
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.
Quote:
Originally Posted by Mikaila31 View Post
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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