I'm going to break my cardinal rule and opine about a species I've never actually kept: To my knowledge, few parrotfish actually feed mainly on live stony corals. They will scrape around the coral colony edges to get at algae, and in the absence of other food may go after coral itself. Some feed on thallose algae or even detritus. We've all seen those pictures of mound corals with huge scrape marks on them from parrotfish - not sure the circumstances of those photos, but I've never seen that myself diving in the Tropical western Atlantic.
That said, I agree with saltwaterstart - this fish will grow too large, even for this person's 600 gallon tank, it will crunch up every non-coral surface, and will excrete lots of that as nasty sediment that will cover the corals. No fish (except Bermuda chubs) poop more than parrotfish.
JHemdal
BTW: Two people with avatar pictures of left-facing LSD's is a bit confusing(grin)