Unhealthy fish. . . .help please
Alright, so i like to believe i know my way around a fish aquarium so when a co worker of mine approached me because she had a newly established tank with a lot problems, I was happy to help. She has a 20 gallon, did everything right setting it up, it cycled for a little over a week, i tested the water and everything looked great, so she added 2 fish, a long finned danio and a glo fish danio. a week later she added a couple more fish. no problems, then she described a white fluffy spot appearing on her fish. I automatically assumed fungus so i told her to begin treatment with pimafix. A few days later it spread, i went to her house to check out the fish, and oh boy was she over feeding, worst i had seen, all you could see all over her tank was extra rotting food, this happened in not quite a 2 week period. i tied the fungus to the the overfeeding, making the water poor in quality. i helped her do a small %15 water change and cleaned decorations, main goal was to get all that extra food out of there. Tank started looking good again, added in a cory cat to help with the left over food. She then calls me to tell me a fish died,( so far lost 4 danio) now describing what sounds like fin rot. i told her to start treatment again. i tied it all together as polluted water caused fungus and snow balling into fin rot. . . .. im not sure at this point. her nitrites were testing a little high so she added a bacteria supplement, everything else was testing fine. This girl is really attached to her fish, doesnt want to kill them. . . . .any help would be great.