Let's hope it's not a tumor, only he is really bloated. Do not feed him for few days. I had similiar problems when I was feeding bettas with too many blood worms. You should try to get daphnia. It works as a laxative and should help you fish poop (if it is constipation).
If it is something else, you can only keep his water clean and warm to make him comfortable.
I have also noticed you add salt in the water with each change. Please note, longterm salt use is not recommended, only for treatmens.
Last edited by roadrunner; 03-31-2011 at 10:21 PM.