I see these posted all the time as advice to newbies and the advice is just not right.
*A side note before reading this: When I refer to ammonia/nitrites being produced by fish, I don't mean fish can produce nitrites. I just mean the overall output of waste that's produced by fish.
Myth: Doing too many water changes will slow down the fishy cycle.
First of all, the bacteria will not grow faster if there is more ammonia/nitrites present in the tank. They will continue to grow at a steady rate in a tank that has 1ppm ammonia/nitrites as they would a tank that had .25ppm ammonia/nitrites. Making these levels higher does not increase the speed of the growth of the bacteria. As long as there is some trace of ammonia/nitrites they can't compensate for, the bacteria will continue to grow.
Second, the bacteria are meant to be grown to have enough to match the amount of waste your fish you have in your tank can produce in one "sitting". Therefore, it is pointless to get the bacteria to grow to a certain point where they can eat a higher amount of ammonia/nitrites than the fish can produce in one "sitting". An example would be, lets say your fish combined produce a steady rate of .25ppm of ammonia/nitrites in one "sitting". Total in one day, they can produce 1ppm ammonia/nitrites. The bacteria that have already grown can match .25ppm of ammonia/nitrites. If this is true, than your tank is cycled. Why? Because the fish aren't going to produce 1ppm all in one "sitting". They are going to produce .25ppm of ammonia/nitrites at one "sitting". The bacteria that have grown to match .25ppm ammonia/nitrites would consume this right after it is produced by the fish, therefore not allowing the tank water to even reach the 1ppm that the fish can produce in a day. It will continue to consume that much 3 more times after the fish have produced it 3 more times. So if you tried to make your tank reach 1ppm, the bacteria that grew to compensate for .75ppm would die off because there wouldn't be enough ammonia/nitrites to keep them alive. So unless you plan on adding a lot more fish that can produce that much in one "sitting", doing this would be pointless.
Thirdly, if you are allowing the ammonia/nitrites to reach really high levels you've created an oxymoron. You're trying to grow more bacteria to "help" the fish, and at the same time you're killing them. At such high toxic levels as 1ppm, you're guaranteed to cause some damage to your fish that would be permanent. And even though you may not physically see any damage, there definitly would have been. Their lives would most likely have been shortened.
Myth: Overfeeding your fish if you are fishy cycling, will speed up the cycle.
This is very similar to the first myth I posted. People say this because your fish will eat more, therefore producing more ammonia/nitrites, and the left over food will rot and produce more ammonia/nitrites. This would make more food for the bacteria, and therefore make them grow faster. This is wrong for the same reason the other myth was wrong. The bacteria will not grow faster if there is more ammonia/nitrites. The bacteria are always going to grow if there is atleast some trace of ammonia/nitrites they can't compensate for, but the amount of "food" available to them does not increase the speed at which they grow. The only thing this would do is #1: kill your fish or severely damage them by making them obese (when fish are obese, they are susceptible to other illnesses) and exposing them to high levels of toxins, and #2: create more bacteria (not at a faster rate) that will compensate for your overfeeding. Once you stop overfeeding them, all the bacteria that grew to compensate for that would die. You should never overfeed your fish for any reason. If anyone tells you this as "advice", I would question any other "advice" this person may have given you.
If in doubt, RESEARCH! There's no better way to make sure that something is correct than to research it yourself. And by proving that something is/isn't true, I don't mean reading a bunch of stuff that says, "you do this because of this" or because so many people said it that it has to be true. I mean, someone REALLY explains to you why it is/isn't true, not just saying, "bacteria will grow faster!". Ask them why. Question the answer. If you do this, you'll almost always be armed with solid advice.
If anyone has any other myths to add that they can thoroughly explain why it isn't true, I'll edit my post and add it to the top.
More info added on Nitrification by RTR page 1.
Myth: Adding salt continually to a freshwater tank keeps the fish healthy by daveedka page 1
Myth: Sea salt in small amounts will kill of ICH eggs by Dahlia page 1
Myth: Holding a fish will burn their skin by YoFishboy, OrionGirl, wataugachicken page 1
*A side note before reading this: When I refer to ammonia/nitrites being produced by fish, I don't mean fish can produce nitrites. I just mean the overall output of waste that's produced by fish.
Myth: Doing too many water changes will slow down the fishy cycle.
First of all, the bacteria will not grow faster if there is more ammonia/nitrites present in the tank. They will continue to grow at a steady rate in a tank that has 1ppm ammonia/nitrites as they would a tank that had .25ppm ammonia/nitrites. Making these levels higher does not increase the speed of the growth of the bacteria. As long as there is some trace of ammonia/nitrites they can't compensate for, the bacteria will continue to grow.
Second, the bacteria are meant to be grown to have enough to match the amount of waste your fish you have in your tank can produce in one "sitting". Therefore, it is pointless to get the bacteria to grow to a certain point where they can eat a higher amount of ammonia/nitrites than the fish can produce in one "sitting". An example would be, lets say your fish combined produce a steady rate of .25ppm of ammonia/nitrites in one "sitting". Total in one day, they can produce 1ppm ammonia/nitrites. The bacteria that have already grown can match .25ppm of ammonia/nitrites. If this is true, than your tank is cycled. Why? Because the fish aren't going to produce 1ppm all in one "sitting". They are going to produce .25ppm of ammonia/nitrites at one "sitting". The bacteria that have grown to match .25ppm ammonia/nitrites would consume this right after it is produced by the fish, therefore not allowing the tank water to even reach the 1ppm that the fish can produce in a day. It will continue to consume that much 3 more times after the fish have produced it 3 more times. So if you tried to make your tank reach 1ppm, the bacteria that grew to compensate for .75ppm would die off because there wouldn't be enough ammonia/nitrites to keep them alive. So unless you plan on adding a lot more fish that can produce that much in one "sitting", doing this would be pointless.
Thirdly, if you are allowing the ammonia/nitrites to reach really high levels you've created an oxymoron. You're trying to grow more bacteria to "help" the fish, and at the same time you're killing them. At such high toxic levels as 1ppm, you're guaranteed to cause some damage to your fish that would be permanent. And even though you may not physically see any damage, there definitly would have been. Their lives would most likely have been shortened.
Myth: Overfeeding your fish if you are fishy cycling, will speed up the cycle.
This is very similar to the first myth I posted. People say this because your fish will eat more, therefore producing more ammonia/nitrites, and the left over food will rot and produce more ammonia/nitrites. This would make more food for the bacteria, and therefore make them grow faster. This is wrong for the same reason the other myth was wrong. The bacteria will not grow faster if there is more ammonia/nitrites. The bacteria are always going to grow if there is atleast some trace of ammonia/nitrites they can't compensate for, but the amount of "food" available to them does not increase the speed at which they grow. The only thing this would do is #1: kill your fish or severely damage them by making them obese (when fish are obese, they are susceptible to other illnesses) and exposing them to high levels of toxins, and #2: create more bacteria (not at a faster rate) that will compensate for your overfeeding. Once you stop overfeeding them, all the bacteria that grew to compensate for that would die. You should never overfeed your fish for any reason. If anyone tells you this as "advice", I would question any other "advice" this person may have given you.
If in doubt, RESEARCH! There's no better way to make sure that something is correct than to research it yourself. And by proving that something is/isn't true, I don't mean reading a bunch of stuff that says, "you do this because of this" or because so many people said it that it has to be true. I mean, someone REALLY explains to you why it is/isn't true, not just saying, "bacteria will grow faster!". Ask them why. Question the answer. If you do this, you'll almost always be armed with solid advice.
If anyone has any other myths to add that they can thoroughly explain why it isn't true, I'll edit my post and add it to the top.
More info added on Nitrification by RTR page 1.
Myth: Adding salt continually to a freshwater tank keeps the fish healthy by daveedka page 1
Myth: Sea salt in small amounts will kill of ICH eggs by Dahlia page 1
Myth: Holding a fish will burn their skin by YoFishboy, OrionGirl, wataugachicken page 1
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