My neighbor has two 10 gallon tanks with like 3-4 rather large (and stunted) common goldfish... and 3 red eared sliders in a 20 gallon. They were formerly in a 10 gallon. She now knows the tanks are way to small, but doesn't want to give any of them up, however she has decided not to replace the goldfish when they die and she will go to more suitable fish. She also plans to get rid of all but one turtle... I wonder if I went over and tested her water for her she might rethink things a little...