Hello, I posted a while ago about the different behaviors of my 4 platy. The two that were acting shy and were bottom sitting stopped after a few days and everyone was normal for a while. About three weeks ago, I would say, I introduced three male guppies and one (if not all) introduced columnaris to the tank. I treated with erythromycin as per the instructions on the box. None of the guppies made it but the platy survived. My black platy, however, has had clamped fins and sits on top of my sponge filter most of the day since then. He gets up to eat when it's feeding time and occasionally swims around a little but that's it. He hasn't gotten worse but he isn't getting better either. My params are good-- 0/0/10 ammonia, nitrite, nitrate-- and all the other fish are acting normal. It's a 40 gallon breeder so they have plenty of room. Any ideas or suggestions? Thank you!