A while back I had a very old FW angel fish. One day one of his eyes was gone. Nothing but a hole - some time later the other one was gone. That was several months ago. I keep a clean tank. Today I noticed that one of my sharks (not sure of the type) has lost an eye! Not merely bulging but it is GONE. Does anyone have and suggestions? Will it continue with the other fish. The tank is 55gal with 2 discus, 2 Silver Dollars, and a few African ciclids. Help - thanks in advance.