[smokinreefer]

No experience with that product, but when you say hes been eating like a pig for 8 months, do you mean you've only had him for 8 months?

What kind of foods do you feed? And how often?
A tang that size needs to eat a TON of food to fatten up.
They are very active fish.

If you're sure it's getting enough food then yeah I'd try treating it.
Again, sorry no input re that medication.