The only other way I've heard of for checking for parasites is if he has odd or frightened behavior, but that may not appear in some fish. I've been told that warming up a pea, then peeling it, then putting it in the tank for your fish to eat can combat parasites. (and constipation?) keep a close watch on the guy, and keep an eye out for any worms or odd stringy poop! If it's a rumor your fish is totally screwed, but tumors are pretty rare. If its bloating or constipation, there are medications from stores and home remedies online. Did that help you?