I guess that depends on the fish and the situation. Nobody knows how fast they'll heal and it varies from individual to individual, fish to fish. My angel is almost completely healed today and I just gave her the last dose. The fin looks full once again except for a tiny peace at the very top. I even considered moving her today to another tank but since I have the extra space I'm gonna keep her in there. Plus moving her will stress her out. so the best answer I could give is......maybe
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It also depends on how bad the fin rot was to begin with. There are a ton of meds out there that you can try that may do a better and quicker job. Melafix is a more natural approach and it's probably easier on the fish in the long run. This is just my opinion. I am a health care major in college (biochem) and meds can really reek havoc on biological creatures. Don't get me wrong, when I'm at my wits end with something like ICK!!! (this stuff drives me crazy) I will pull out the heavy artillery cuz those buggers are hard to get rid of but something like fin rot doesn't have to be a big deal but it could be more, like someone mentioned earlier in this post. i'd guess that going the more natural route could take longer. I saw real improvement in my baby about 3-4 days after. Also, from what I understand, it's very important to keep a clean tank when dealing with fin rot. During the treatment with my angel I actually removed all the gravel! because it had flourite in it that was making everything dusty and she needed a cleaner home. phone ringing bye!