One of my zebra danio's tail seems to have parts of it missing from the top. He was in a 29 gallon tank that is still cycling. I noticed that he wasn't swimming around anymore and just laid at the bottom of the tank. I knew something was wrong so I put him back into my 10 gallon tank that has already been cycled. I have read that good water quality can eventually heal fin rot but when I woke up this morning his tail fin was down to the base! his tail area has a milky color. Please give me some advice. I feel so bad for the little guy.