I did not realize that your water was already heated. I don't really know anything about RTCs. If your water is all ready heated, then we know that it isn't Cold Water Fish Pox that most of the time only comes around when the water is colder, and then will go away with heated water. I have a few koi with this. If it really is fish pox, the only way to get rid of it is to destroy the fish, and bleach all of the remnants of what he was in contact with. BUT, Fish pox is really nothing to worry about. It won't kill your fish, it will just make him ugly. And yeah, feeders aren't the food of choice, as they carry many things- Fish pox is not know to be contagious though.