I have a tang, and i've had him for about....3-4 weeks now...he is with a Valentini Puffer, 2 Clowns, Mandarin Goby.....and thats it fish-wise...there is about....100-110 Pounds of LR in the tank now. And I just started to notice my Coal tang is getting a little lighter, and i'm not sure if he is sick, or whats happening. Anyone know?