For a gallon dosage, dissolve 1 tablet in 10 tablespoons of water.Add one tableWait 4 days before you do a second dosage. spoon of concentrate mixture to one gallon of water. This info came from Healthybetta.com. I hope this helps!
Most petstores ought to have JFC or JFE. Walmart or Petsmart might have it. Melafix can be used to treat other fish. I think bettas are like people and some are more sensitive to medications than others.
He became lethargic pretty much right away. I just read Kim's response to your question. I also have heard that Melafix can damage a betta's labrinth organ. I'm afraid to try Melafix again but have had no problem with Bettafix or JFC or JFE.
I haven't really heard any good things about Melafix. I used it on one of my bettas once and he became very lethargic and looked miserable so I took him off of it. BettaFix is the same thing only milder. I've had success with it before, for fin rot.