clean water
many times fin rot is related to water conditions(not always the case as fin rot is a very general term)
usually the addition of anti biotics is to offset secondary infections caused by the damage from fin rot.
in some cases severe bacterial infection as a result of the rot.
in some cases fin rot is Sx of another issue..which may not be resolved with addition of any anti bacterial medication.
I doubt it'll really help much if the case was bacterial infection rather than wounds.you could try melafix it is good stuff