[HaremShaih]

I can't shed any light on it either, apart from saying it doesn't appear to be caused by any damage when very small, as the skin and scales look fine. As Teleost say, probably just a mutation which could be "natural" (as opposed to being caused by polution or disease in the parent fish from where this fish was spawned).

And likewise, if you're new to these forums and not a refugee from the old place, welcome.