Let me start by saying I'm not sure it's an infection but I'm curious how long (ballpark) should it take for an infection to run its course and be in the clear. If I didn't see the brown blotch on him in 2 spots I'd think he was perfectly healthy. He's showing no signs of anything. Eats good swims around plays in the powerhead. A happy fish.... but that mark. I'll post a pic again but I've already had a discussion about it and the consensus was an infection. Melafix has been in the display tank for 2 days I hope it at least helps and nothing in the tank has responded negatively to it. I know in humans you can let it run its course in a couple days and it can either get better or get much worse and need antibiotics ( I've had mrsa after 2 days it was to the doctor). Is this the same in fish. If a couple days passes and it's not getting worse is the fish fighting it off or can they take much longer. Not familiar at all with the immune capabilities of fish.