I have a citron goby that used to be all yellow but lately i noticed he had a small spot on his tail that was all black and it wasn't raised up or flakey. It later turned into half of his tail over the course of a few months but he still acts normal and eats well. It just looks like the yellow turned black. Anyways I treated him and nothing happened to the area. So i'm just wondering if some fish get black pigment or if he has some disease or something that isn't very common?
Thanks
Thanks
