Not to disagree with Blair because I know he has many years more than I do in fish keeping for sure, but I don't feel Melafix is snake oil by any means. While I do feel there are a lot of "meds" that simply don't work as advertised Melafix is not one of them in my opinion.
Reason I say that is this- Just this past December I had one of my frontosa get beat up so badly by one of the other fronts (he no longer is with the front tank and lives in the mix African tank these days because of his attitude) anyway one of them got so beat up I feared I would have to put him down. His fins were all but gone and worst of all he had white fluffy fungus over 20% of his body on the wounds. I did daily water changes for the better part of a week with no change at all in the white fungus. As a last ditch effort I went and bought some Melafix and added it one evening. The next morning all but a slight amount of the white fungus was gone, and with in 48 hours it was all gone. His fins grew back to where you can't hardly even tell he ever had any issues. I don't think the Melafix did much to help his fins grow back, that's just natural fish regrowth there most likely, but there's no doubt that the Melafix did help rid his wounds of the white fluffy fungus. If that were an isolated incident I would maybe say it was just coincidence, but I also had pretty much the same thing with an Eye Biter I use to have where the Melafix got rid of his white fungus on a wound with in a day as well.
Granted Melafix does not look like much from the ingredients - 1% cajeput oil, 1% emulsifier (Crovol PK-70 nonionic emulsifier)0.2% defoamer (FG-10 by Dow Corning) 97.8% deionized water" ...so doesn't seem like there's much in the way of "meds" in it, but it's hard for me to say it didn't help after the experience with my one Frontosa and Eye Biter I had with it.
Just my .02 for what it's worth.