Beneath is a photograph of Zeus, who has marked swelling around the anal opening. The fish had been in hospital for about three weeks due to an injury to the fin and side I thought was caused by an aquarium ornament. Treated with water changes and melafix. One week into quarantine, developed what seemed to be symptoms of flukes (loss of appetite and continued flashing), so I treated with praziquantel, figuring that I had misdiagnosed the cause of the injury and that it was actually the result of earlier flashing that I had failed to notice. Fish did fine on recommended dose of prazi and side and tail were completely healed when I reaclimated him to the main tank last week. As you can see, he now has what looks like a protruding anus. There is no flashing activity or any other symptom of parasites. Eliminating normally and shows no signs of victimization from other tankmates. I'm sorry for the horrible pictures. The photo makes it look larger than it is. Any guesses? Some parasite that was not intially knocked out by Prazi?