Goby with Red Sore on belly (advice)

[Stanley11]

Need help. My goby has a 2 small red sores on its belly and he is not acting right. Lethargic and not eating that much. Treated with Melafix with no success. Any advice for an antibiotic for treatment? I am at a loss of what to do. I should note my chances of actually catching him are low. Any recommendations for a treatment. He is in a tank with invertebrates and corals. Thanks all.

[L8 2 RISE]

Pics would help, as would more info about the fish and the tank- how ling have you had him? Other fish? Parameters? Etc etc

[s2nhle]

He may get coral stink.

[Coral Hind]

Do you have fine smooth sand or course rough stuff on the bottom? If it isn't a fine substrate they can scratch their bellies and get an infection.