@MattsBettas - I hadn't considered that; I can try just doing regular water changes and stopping the epsom salts, and see if that helps. I'm not sure what you mean by a "proper" quarantine tank, though. This one has heat and an airstone, and does get the water changes every other day.
@LittleBlueFishlets - I've been using the Maracyn for about two weeks, as callistra suggested to me in my original thread. I just changed his water today and didn't put any Maracyn in.
@callistra - Two teaspoons of Epsom salts per gallon, and I've stopped the Maracyn now. His poop is a reddish brown, which is about what color his food is, so I'm not too concerned there. There isn't any white or fluffy stuff in the tank.