He is in a community tank with other sevs and juvies which is where he has been for a few months. I haven't checked water....stopped checking routinely a long time ago. Plus I do 30-50 % changes on that tank every other day as I have a lot of juvies in there. This has been going on amost since I got the fish. Nobody else in the tank is affected. It has always looked just like it looks now...the spots have just gotten bigger. Explain what you mean by ulcer...to me that implies injury.