Poor thing. The only thing you can do for him is to keep the water as clean as possible--aquarium salt will help, and you may want to treat the water with a small amount of methylene blue to help prevent secondary infections. If you use methylene blue, you should do so in another container since it can be very harmful for invertebrates and plants.
I use rubbermaid/sterilite plastic storage bins from walmart/target. They are only about $3 each and are very durable and safe for fish. They can be safely heated, also.