I used to work in Aquatics and had tanks at home, one with a beautiful black moor goldfish(fancy tail, big eyes, short and stubby you know the sort), it started off black and as most untrue fish turned orange. One day someone bought me in this Pangasius cat fish, lovely little 4 inch black fish with the most gorgeous whiskers out, and in he went with "Dudley" the black moor. They lived happily for a short while until one day on a quick glance passed the tank, poor Dudley appeared to have lost one of his eyes, frantically searching around the tank for sharp objects and the gravel to see if I could see it(excuse the punn) Mr. Catfish proudly swam passed Dudley and whipped out his other eye. I never thought to look in his mouth for sharp objects. Poor Dudley kept swimming unrelentlessly hitting first one end of the tank and then the other and his loss did not bother him at all, but I could not stand to look at his poor gazeless face any longer and had to get rid of him. Aaarrrhhhh