RIP Knuckles
Clipper and He were in a divided 30l tank. I think the cycle broke down and that allowed them to get fin rot. Clipper had it worse yet he got over it in a night. Knuckles didn't have much at all but I still treated him for it using Melafix, which I've since learnt not to use on Bettas. But it was too late, Melafix is thought to affect the labyrinth organ which Bettas use to breathe air from the surface.
I moved him to a smaller tank so he could have clean water every three days and be treated with salt. His fins were fine but I could tell he was having problems breathing he was gulping at the surface constantly. I came upstairs one night and he was lying on the floor of the tank. Getting him out of the tank was one of the most horrible things i've had to do so far with my fish. Taking out a dead tetra or two is completely different to a fish that recognises when your in the room and swims up to you for some attention.

