, I would take it back to the LFS
and say that you did not realize it was so aggressive and an expert-only fish that will require such a large tank. My thoughts with stuff like this is that if you have to ask, you are not an expert and the fish really does not stand much of a chance. Better to admit that you are probably in over your head (which I'm sure we've all probably done in this hobby) and try to save the fish. Please don't take offense...I've been in this hobby for a long time and there are still certain things that I will not take on. Expert-only is out of my league.
I also saw you had another thread asking about Ich on a Hippo Tang. What size tank do you have? How's that fish doing and how did you treat it?