I have a pleco that had fin dammage after getting very stuck in a cone feeder in the tank. Ripped quite a bit of fin (not the same as fin rot mind you) and I kept the tank extra clean and I believe added some melafix just for the heck of it. Within two weeks no rips/full length/happy guy. It was far more rapid then I would have believed - they have such healing powers when things are right for it.