I have a tiger oscar that is probaly around 7 inches long and he is turning gray! He has been like this for about a month and I asked my dad about it and he said hes fine and not to stress so much. Its not his whole body! Its on his head. Its been progressing and now his back is gray now also. He still acts the same, eats well, and swims around alot. Idk if its because he is growing bigger or unhealthy diet. But I have feed him all sorts of stuff to pellets to shrimp. This is my first time keeping oscars so I wouldnt off the bat know what it would be. If you know what it would be please tell me, Thanks!