Water change

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You are probably right about 20% not being enough, but your "math" is simplistic and misleading. The size and frequency of water changes is primarily dependent on bioload. The quality of the water source also may be a factor. For a very lightly stocked tank, 20% may be enough. On the other hand, I have a friend with a heavily stocked tank that requires a 50% water change every other day.
I have a couple of smaller (5 gallon) tanks, they do well and don't accumulate nitrates as quickly as some of the larger tanks I have. This is like you said, due to bioload and amount of plants or extra filtration that intake the bioload waste.

Overfeeding can lead to needing more water changes as well.
 
You are probably right about 20% not being enough, but your "math" is simplistic and misleading. The size and frequency of water changes is primarily dependent on bioload. The quality of the water source also may be a factor. For a very lightly stocked tank, 20% may be enough. On the other hand, I have a friend with a heavily stocked tank that requires a 50% water change every other day.ealthy
Hello. Ideally, you should keep the number of fish to a minimum. But, the most important thing about water quality is maintaining all the mineral levels in the water. The longer the same water stays in the enclosed cube, the more it changes chemically. The fish and plants will remove nutrients from the water and elements that make up a healthy water chemistry are changed in the presence of oxygen. The process is called "oxidation". So, you can have the right number of fish in the tank, but still have less than optimum water conditions. By removing and replacing most of the tank water weekly, you can remove toxins and replace nutrients.

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One of the things I learned here that sticks with me is that we don't do regular water changes to fix bad water parameters. We do regular water changes to keep the parameters stable so that they never get bad.
I think of it like mowing the lawn. Mowing the lawn is a good way to fix tall grass. But doing it every week keeps the grass from getting tall in the first place and avoids all those problems.
 
By removing and replacing most of the tank water weekly, you can remove toxins and replace nutrients.
Again, misleading. This depends on the quality of the water source. The part about "nutrients" is simply wrong. There should be no nutrients in your water supply, unless you are referring to calcium which fish require for skeletal development.

As for "toxins" whatever toxins you are referring to are removed along with the nitrate, and this can be done with 20% weekly water changes assuming a light bioload. Using a lot of ambiguous words to defend a preconceived belief or a poorly developed argument is all too common on Internet forums, and one of the primary reasons for all the misinformation being spread in this hobby specifically.

Again, I'm not arguing against larger water changes. I'm simply stating trying to make it clear that there is no general formula that is applicable under all circumstances.
 
Again, misleading. This depends on the quality of the water source. The part about "nutrients" is simply wrong. There should be no nutrients in your water supply, unless you are referring to calcium which fish require for skeletal development.

As for "toxins" whatever toxins you are referring to are removed along with the nitrate, and this can be done with 20% weekly water changes assuming a light bioload. Using a lot of ambiguous words to defend a preconceived belief or a poorly developed argument is all too common on Internet forums, and one of the primary reasons for all the misinformation being spread in this hobby specifically.

Again, I'm not arguing against larger water changes. I'm simply stating trying to make it clear that there is no general formula that is applicable under all circumstances.
Hello. I understand that water supplies may differ. Here, we generally have water that's high in minerals and trace elements that the fish take from the water to maintain good health. If we allow the same water to remain in the tank, then the fish use up those nutrients and aren't as healthy. The more water we change and the more often we do, the healthier the fish. Now, your situation may be different where you live, but the fish in my tanks would prefer I change a lot of their water frequently than a very small change less often.

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This seems a contentious subject. I am a newbie and generally ignorant of all the minutia. Until this week Linda or I tested every morning. We do about 30 percent every four days. Sometimes a bit less and sometimes a bit more. Gravel vac each third change. Our tanks seem to have settled at 0 - 0 - 10.

We did lose some fish early on but thanks to the people here we resolved some issues.

Again, I stress, we are ignorant of much but it does seem water changes are critical based on reading and early results.

Much to learn but good maintenance seems to be basic to all else.
 
Again, misleading. This depends on the quality of the water source. The part about "nutrients" is simply wrong. There should be no nutrients in your water supply, unless you are referring to calcium which fish require for skeletal development.

As for "toxins" whatever toxins you are referring to are removed along with the nitrate, and this can be done with 20% weekly water changes assuming a light bioload. Using a lot of ambiguous words to defend a preconceived belief or a poorly developed argument is all too common on Internet forums, and one of the primary reasons for all the misinformation being spread in this hobby specifically.

Again, I'm not arguing against larger water changes. I'm simply stating trying to make it clear that there is no general formula that is applicable under all circumstances.
🧐 less of the hoity toity please, its unnecessary.
 
🧐 less of the hoity toity please, its unnecessary.
I stand by what I said. Some of the comments made here are simplistic and misleading. The wording is ambiguous at best. For example, exactly what "toxins" is the poster referring to? It's as if he's waving a magic wand to support his (false) statement in addition to ignoring simple logic. Whatever "toxins" exist are leaving with the nitrate.
I thought this forum was dedicated to presenting facts rather than Internet opinions. If that's not the case, I'll happily leave. No point in wasting my time.
 
There are a few points here that people are getting strangely abrasive about.

I have never had chloramines, and always chlorine. In a run of the mill tank, you can gas off the chlorine by pouring the water into the tank with force. The chlorine will dissipate.
I didn't use dechlorinators for many years. I use the API stuff now in certain tanks, because I found with the gas off method, breeding was affected for a couple of days after a water change. Given that I water change tanks weekly, 4 days a week was not good for egg collecting.
Most of our disagreements come from the devil being in the details we forget to mention or take for granted.
So I dechlorinate all tanks in which I hope for breeding, for all species and groups. Most hobbyists don't breed fish, so @plebian 's point is one I'd agree with. Almost. Mostly. Not always.

20% is better than nothing, and is a basic level that works. I prefer more, even in lightly stocked tanks. If I go beyond 30%, I dechlorinate in all tanks.

Source water IS crucial. Some of the water out of taps in rural farming areas is awful stuff. The water table is polluted in a lot of places. How people in those regions manage their water is radically different from how I would. My water comes from a protected watershed and is very clean. I know that's a luxury, and I sometimes catch myself up when I post here because I do try to remember I'm fortunate.

The internet is what it is. If you state something and back it up, you're accused of being too serious, and going on and on. If you state something and don't back it up, you have no credibility and could be passing along myths.
 
It is an interesting thread with a lot of emotion. Some of what is here is useful to people like me and some. Is far too academic for a casual hobbyist.

Linda and I are enjoying the fish and the process but have not to much interest in the underlying biology except in methodology to fix issues as they arise. Each solution then goes into the memory bank.

This thread now reminds me of a class the college forced on me. I was in my early 40’s and had reached a point where I needed more alphabet behind my name career wise. At the time I managed almost 300 people. Anyway …

To attain the particular degree required a particular math course. I had no real issue, I have a mathematical mind. I took the exams received the grades until the end of the year. Aced the test but received a poor grade. Asked the professor why and was told I did not show my work. I never had. I explained that in truth I did not know how I processed the problems, I just knew the solutions. Was told and I quote, “you will need this someday and will need to know how”. My reply … no sir. If this ever becomes a critical function in my work I will hire somebody like you.

The moral is that sometimes, more often than not, the minutia is best left to those suited for it. The second point is it is important to understand no solution is ever universal in the real world.

Sorry for the sermon but one of the things I really like on this forum is the smoothness and while great minds, and there obviously some here, can disagree “testiness” winds up being non informative.

Good day to all.
 
I will note that sometimes a forum, the printed word, gives false impressions because a conversation is more than just printed words.
 
It's complicated because we discuss here. If I say to you to do 50% water changes weekly, and go on about unknown toxins, or if I put my hand on my hip, wag my finger and sing "I'm gonna tell you how it's going to be", you, if you are new to this, may follow bad advice. What fish you have or want, your water, your tank size, your work and play ethic - all these things add up.

Your math example is a good one. You arrived at the answer without showing the work. But if you tried to teach me, I would want to see that work so I could understand too. If someone asks a question that shows they've just started up, then seeing the work lets them decide where they're going in a more informed way.

Questions should generate questions, and answers can be dead ends.
 
It's complicated because we discuss here. If I say to you to do 50% water changes weekly, and go on about unknown toxins, or if I put my hand on my hip, wag my finger and sing "I'm gonna tell you how it's going to be", you, if you are new to this, may follow bad advice. What fish you have or want, your water, your tank size, your work and play ethic - all these things add up.

Your math example is a good one. You arrived at the answer without showing the work. But if you tried to teach me, I would want to see that work so I could understand too. If someone asks a question that shows they've just started up, then seeing the work lets them decide where they're going in a more informed way.

Questions should generate questions, and answers can be dead ends.
Good points. Sometimes the give and take on a forum gives the false impression of “testiness”.
 

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