My fish has developed a patch of red on his belly. It looks like a lot of tiny little red spots together. At first I thought it was a wound so I treated with Melafix. Now the red patch is gradually spreading down his belly towards his tail. He also seems to be rather lethargic except when I feed him.
The tank is 10 gallons, and I did a 40% or 50% water change several weeks ago. I probably can't get the tank specs until Monday.
Any ideas on what this is and the proper treatment for it?