Originally Posted by jaysee
This is absolutely 100% not true. There is ABSOLUTELY NO harm in doing massive water changes on a cycled tank. For some reason this misinformation continues to be propagated though, despite all evidence to the contrary.
There are still people that think the world is flat (flat earth society) so I'm sure we will continue to hear this for some time to come.
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I am sorry. I should of worded this more carefully. Rarely be done in a cycled tank. This is because I have done it before without knowing the consequences. I thought that all tanks needed biweekly 100% water changes. I knew that Beneficial Bacteria live on all surfaces in the tank(which is what is right) I thought that doing the change wouldn't harm anything. I had just finished a fishless cycle. It was a HASSLE taking out the fish and putting them in containers. Then, I removed the tank water. I lugged buckets back and forth to refill the 10 gallon tank. I filled it with dechlorinated water. I then had to wait for all of the fish to reacclimate to the new water temperature. Then, about 3 days later, I started to see signs of sickness (which I did not know what they were at the time) I tested the water and saw that the ammonia levels were too high (above the normal levels of 0). I was shocked as I thought that my tank had been cycled. Turns out that my ph levels, hardness levels, and ammonia levels in my tap water had changed. I guess my city had been adding ammonia to the tap water recently, and along with my partial water changes, that level had built up. I didn't drip acclimate my fish. One of my fish died
but the others eventually were treated but I was just trying to say that 100% water changes are way too much of a hassle. There is no need for them in a cycled tank, unless you like all the extra work!
(Unless nitrates are severely high!) I do know that BB lives on aquarium surfaces, and not in the water column.