I tried melafix. Every time I put it in the tank, the kuhli loaches frantically swam against the glass like they were trying to escape. =( My platy died last night. Maybe he was sick with something else as well because he was very stiff and was just floating at the top of the tank and breathing heavily. His tail fin wasn't that badly hurt, but was a bit ragged at the edges. Thanks for the advice, but I guess it was too late for him or maybe I misdiagnosed the problem. =(