I have a Naso Tang that I've had for over 6 months and within the last month he has started to lose over 1/3 of his weight and he's still losing. His appetite is great and has a few off days where he doesn't want to swim. Will eat seaweed perfectly fine. I just recently saw that one of his eyes had a white piece of skin I would say coming out of the inside of his eye. I honestly don't know what's wrong with him. Does anyone have any advice?