He's in a 4 way divided 10 gallon that's filtered and heated. The dividers are black mesh so he can't see his neighbors, and there are live plants. I don't have anything but regular aquarium salt on hand-- I've just been trying to avoid stressing him out as much as possible.
Yesterday he refused his food, and I think he may pass today. I woke up to him on his side at the bottom of the tank, breathing rather hard and staying limp. (normally even while i'll, he gets up when I come over, zoomes up to breathe, and waits to be fed.) Idistrubed him gently with the net because I wasn't sure if he had passed or not, and realized that he was almost unable to swim. So I cupped him in a petco with just water from the tank and am floating him in his section so breathing will be easier. I had to actually net him, since he wouldn't come to the surface for my cup. It was so sad-- except when he was out of the water, he didn't even bother to struggle against the net.