He's gone that dark probably for the past month? He's eating fine and swimming about as normal, so I really don't understand it? He is my biggest cory and one the first I bought. He was always a little darker than the other one but not by that much.
I bought those two (leucomelas) but couldn't get hold of anymore to bring the number up as I wanted to get 4 of them. So in the end I got 2 trills and 3 pandas to accompany them, they all get on fine and shoal together happily. At first I was worried that he became a little lethargic as he seemed to just sit on the gravel alot, however as I've been keeping a close eye on him lately he seems to be fine, swimming around both on the substrate aswell as the middle section of the tank and rummaging excitedly for food once it's been put into the tank.
He is probably my most chilled out cory though, the other one of his species does tend to have it's crazy moments of going up and down then glass etc but he doesn't seem to anymore? I'm saying it's a he like I know but I don't actually lol, could be a he or a she! I can't see any evidence of illness in terms of appearance other than him changing colour!
Amy xx