Originally Posted by Angelmonster
Personally I would not use tank water. If fin rot is involved i prefer to gave a quarantine tank available to keep him in. Who know what will be left behind in the tank if the fish is sick. :-/
I would do a mixture of tank and treated fresh then with more treated fresh than tank. If the fish freaks in the salt bath it has extra stress on it, even though dirty tank water is "home" now mixing in fresh water to dilute the dirty while you water change the tank is a good idea.
If the fish is fine in the salt bath then none of this extra is needed ;)