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I wanted to show you this black colour variant of Corydoras sterbai. This 3,5cm long fish is three months old. The strange thing is it has grown about 50% faster than the normal colour variants from the same batch. Both eyes are weakly developed. I don't know if this one is a result of inbred parents or a spontaneous mutation. The twenty other fish seem to be totally normal. This mutant specimen is doing very well and I am going to keep it, but of course I won't let it reproduce.

It's head's a funny shape too. Odd looking thing all round.

this is a rare one. i kinda like it
btw, do you have a high surviving rate of raising your sterbai fry?

I have seen this before, but not very often. This is an almost black C. sterbai that came from one spawning about three years ago. It is a little smaller than a normal adult but is fully formed.

C. sterbai (Black)

Image courtesy Ian Fuller & Corydorasworld

Now they are weird. is it me or do they both have smaller than normal pectoral fins too?

The aquarium strains of Corydoras sterbai have begun showing several traits I believe are related to considerable inbreeding.
The black color is a new one but Ian's specimen of his dark one also shows a shorter body, more chunky than normal or wild fish.
The fact that albino C. sterbai are now another established aquarium variation is another indicator.
I expect long finned variations to appear soon if they haven't already.
I get a few per cent of normal colored C. sterbai with the foreshortened body like Ian's example, although their eyes are normal, from every 100 or so fish.
I have been destroying them as they become apparent.
I wouldn't encourage preserving these dark fish. Maybe a melanistic form with normal morphological development but not these examples.