finrot treatment?? anyway, lets try and figure out why your fish has finrot in the first place shall we? WHat size tank is it and are there any other inhabitants? is it filtered?
also some water stats would be useful. when was the last water change you did? finrot is caused by bacteria, something you get a lot of in an unclean aquarium.
go and do a 60% water change, get some meds and start dosing, good luck!