I know you're upset. Call your local pet store. They can advise you of anything you can do for him. You may need to separate him from the others, as Audrey suggested, even if you just get a divider to section him off from the other fish in the aquarium. I don't know if they make antibiotic drops for fish, but maybe. I would definitely check with people who see these fish. I hope he'll be ok, Gepansy, but if he isn't, I hope he won't suffer. That's exactly why I don't have fish!!! Can't stand to see them suffer.