Join Date: Oct 2010
Location: Victoria, Australia
Personally, I don't believe Bettafix is harmful to bettas. I know a many hobbyists who use it without any issues, and remember correlation does not equal causation. I think the issue with Bettafix is that when used to treat serious ailments, it's like putting a band-aid on a severed limb. It's not a miracle cure, and having used both Melafix and Pimafix in the past, I don't think any of the '-fix' treatments do anything more that clean water, time, and a high-protein diet won't.
Okay I must have missed the opening sentence in your post. I see now you want to use it to treat fin rot, but my advice remains the same.