salt stings but thats cuz its helping the wound...when you get a cut and go to the hospital they rinse it with a saline solution to clean it, when i worked as a vet if a dog was cut or had an open wound we'd flush the wound with saline... which is just salt water, sometimes 10 times a day. the salt, i know for terrestrial animals is beneficial to the healing process, and i put salt in my catfish tank all the time just because i believe it helps with there colors some, helps reduce stress when moving things around in the tank and just all in all makes them happier. its completely up to you, hes your fish im just saying what i know. i really hope hes ok though, i love tsn's