I am going to try and catch him tomorrow, but I don't know how to treat him.
He has two white patches that have slowly got bigger on one side, in one of the white patches a hole has developed and you can see his flesh.
Do you think it is some kind of fungus and what should I do he is swimming and eating ok but I am worried the hole will just get bigger and kill him.
I have had him for a couple of years.
Any ideas can't take a photo he won't keep still.