[DiverDude]

From what I've been through in the last few days, I think it was a good move to get him out of the tank. Given his condition, I'd consider some form of anti-microbial treatment (Prazipro, Copper) and see if that does anything.

Offer plenty of food and soak it in vitamins and garlic.

If he's gasping for air, you can try and help by oxygenating the water as much as possible by adding an airstone and/or pointing a power head upwards so it disturbs the surface.

It's difficult when you don't know for sure what you're trying to treat and from the sounds of it, he's in pretty rough shape so do what you can and hope for the best.

Good luck.