Comments pls on my water change amount

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Steven 1

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Hi. I was wondering if I could get some comments on my water change amount. I suppose it would be useful to look at my test results. Before the last water change, pH was 7.6, KH 1 dKH; GH 2. Substrate is MGOCPM + sand.

I have been changing 50% per week, and that has worked well, but now I have the dirt substrate and it seems to me that 25% would now be appropriate.

Please let me know your thoughts on the subject.

Steven
 

Byron Amazonas

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Steven, those test results are not closely related to water changes; before or after a water change the GH and KH should remain much the same [there are exceptions as when one is deliberately adjusting these]. The pH will not likely change more than a couple decimal points, although if the tank is not biologically established the pH can fluctuate and the water change would help to restore it, even if temporarily. Some people use nitrate as a test for needing a water change, but this is risky because the aim should be stability, not as a reaction to trouble which is like closing the barn door after the horse has bolted.

Some advocates of soil substrates suggest no water changes at all. But one must remember that these same sources also have heavily-planted tanks with low to moderate fish loads. The more fish, or the larger or more active the fish, the more impact they create on the system. And while plants can handle this, there is a limit.

Water changes in low-tech planted tanks are said by some to be detrimental to the plants, by increasing the CO2 temporarily. I care more for my fish than the plants, so I have always done regular weekly 50%+ water changes and my fish have responded positively, and I have not seen any detriment to the plants. If we could replicate nature where the fish are constantly in "new" water, it would be ideal. But that is not feasible in the home aquarium so we aim for the next best thing which is regular water changes, and the more water changed the better for the fish. Water stability will be more certain.

Byron.
 

Steven 1

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mgamer: I think that in my 10g tank with a dirt substrate 25% water change is now more appropriate than my previous 50% per week for several reasons: first of all, I use a 5 gallon plastic bucket to pour new water into the tank, and I'm used to 2.5 gallon increments; and more importantly, because I surmise that water changes result in leaching the nutrients out of the dirt over time. So reducing the amount of water being changed ought to extend the nutrient life of the dirt substrate.
 

Steven 1

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Agreed, except for the CO2 thing - I could aerate the water overnight if I wanted to. Btw, as an aside, I think aeration degasses tap water but tank water should be near atmospheric equilibrium already.
 

SnakeIce

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That assumes no nutrients are in your water, which is highly unlikely. I notice better plant growth in the half day right after I change water, so changing water isn't necessarily a bad thing and could even be beneficial to your plants and your fish.
 

Steven 1

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SnakeIce,

My tap water is very soft - have to use Seachem Equilibrium to bring the GH up to 5 dGH.
 

Byron Amazonas

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Agreed, except for the CO2 thing - I could aerate the water overnight if I wanted to. Btw, as an aside, I think aeration degasses tap water but tank water should be near atmospheric equilibrium already.
There are two schools of thought on the CO2/aeration issue. I had a private discussion with Tom Barr on this some time back, when I first noticed some sources (articles in TFH and such) beginning to recommend aeration to increase CO2. There are to my knowledge no determinable studies yet on the results, and the atmospheric aspect was Tom's main point too.

I assume your "agree except on the CO2" is in reference to my previous post. Tom's point was that there can be a lot of CO2 in tap water [you can do a pH check of your tap water straight from the tap, then after vigorously shaking it, to see the difference if any which will give you a rough idea] and this enters the tank with the fresh tap water. This gets used up or dissipated over a period of hours, after which the CO2 is at a lower level until the next water change.

You do not want to aerate too much overnight, unless you have a CO2 problem for the fish. The idea behind natural or low-tech systems is to allow the CO2 to build overnight so the plants can use it when the light comes on. I have been experimenting a bit with increasing surface disturbance, and things have actually improved. Of course, this is permanent, the disturbance I mean, day and night, since it is due to the filter return agitating the surface a tad more than previously. I went to this because I did actually notice some of the fish respiring more after the lights came on, and increasing the agitation has resolved this, so clearly there was a CO2 imbalance. This is something you will just have to be aware of and keep an eye on, when fish are in the tank; the whole benefit of soil is initial CO2 production, so obviously this will be significantly greater (or should be) with soil for the first 6 months or so.

Byron.
 

Steven 1

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There are two schools of thought on the CO2/aeration issue. I had a private discussion with Tom Barr on this some time back, when I first noticed some sources (articles in TFH and such) beginning to recommend aeration to increase CO2. There are to my knowledge no determinable studies yet on the results, and the atmospheric aspect was Tom's main point too.

I assume your "agree except on the CO2" is in reference to my previous post. Tom's point was that there can be a lot of CO2 in tap water [you can do a pH check of your tap water straight from the tap, then after vigorously shaking it, to see the difference if any which will give you a rough idea] and this enters the tank with the fresh tap water. This gets used up or dissipated over a period of hours, after which the CO2 is at a lower level until the next water change.

You do not want to aerate too much overnight, unless you have a CO2 problem for the fish. The idea behind natural or low-tech systems is to allow the CO2 to build overnight so the plants can use it when the light comes on. I have been experimenting a bit with increasing surface disturbance, and things have actually improved. Of course, this is permanent, the disturbance I mean, day and night, since it is due to the filter return agitating the surface a tad more than previously. I went to this because I did actually notice some of the fish respiring more after the lights came on, and increasing the agitation has resolved this, so clearly there was a CO2 imbalance. This is something you will just have to be aware of and keep an eye on, when fish are in the tank; the whole benefit of soil is initial CO2 production, so obviously this will be significantly greater (or should be) with soil for the first 6 months or so.

Byron.
Thanks for the info, as usual, Byron. It seems a little difficult to discern what the aeration is doing with the CO2 - whether it is increasing the amount of CO2 or decreasing it (fish respiring at the surface, surface agitation fixing that) to me, anyway and I'm sorry for not being clearer - I meant that I could aerate the new water in the bucket to be used for the water change the next day (a common suggestion) overnight if I want to, avoiding some of the CO2 peaks from undegassed tap water. Btw, I have adopted the practice of stirring the tap water until it becomes clear. I assume that this does something to de-CO2 the tap water.

I think that aerating the tank forces the water to dissolve more atmosphere (with a corresponding higher dissolved atmospheric pressure) including CO2. Or maybe I'm looking at this the wrong way, and it attempts to de-gas tank water and you get less dissolved atmospheric gases. Uh! Lucky if I get out of this with all my feathers intact. Sounds like it depends on what the dissolved atmospheric pressure is vs. the equilibrium dissolved atmospheric pressure. If there are more atmospheric gases dissolved, aeration would, it seems to me, try to release excess gases. Conversely, if there are less dissolved gases than the equilibrium point, aeration would help bring more atmosphere into solution. It seems to me that any water movement would release gases, including CO2, at night when more of the dissolved bacteria-generated CO2 is building up, and that the dissolved gas level is always trying to get back to equilibrium with the atmosphere.

And, to wrap things up, it seems to me that in the typical situation of fish gasping at the surface, the fish might be having trouble breathing because of too much CO2. I'm not sure. Probably not in a low-tech tank. Low water circulation not bringing enough O2 into the tank?

Steven
 

SnakeIce

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I have read that CO2 can be higher without causing distress, as long as there is sufficient O2 levels. I don't know/remember if this follows a ratio or if it is completely independent though. Of course this is within reason, with pressurized you can pump in enough to kill fish.
 
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