urgent yellow tang question

[loyalty]

hey everyone, I've got a question for a friend that doesn't have computer access. He has a 75 gallon tank that is fish only w/ live rock. We started our tanks at the same time; tanks going about a month or so.

-In his 75 gal tank, he has about 80lbs olf LR
-he recently bought a yellow tang that was fine for a few days, but now it hides and slinks along the bottom of his tank.

-he says his water parameters are fine, but I've noticed the tang hides a lot(i.e. all day), hangs out at the bottom of the tank, and isn't eating. Any ideas?
Thanks

[MonoSebaelover]

He added the tang WAY too early. In general one should never add a tang to a tank under 6 months old due to the unbalanced water quality because the tank is too young. There could be ammonia or nitrite present or it could have ich on it (little white looking dandruff all over the body). Anyway, hope this helps and good luck.