Not only do they get huge, they definitely are coral eaters... and they are not very picky. They will munch on just about any coral you have. I made the mistake early on of putting a small Pineatus in my 46 gallon reef. I had to tear the tank apart after about an hour because he was feasting on every coral in the tank. It was a Batfish Smorgasbord. A little taste fo this here, and a little taste of that there....
Definitely not a reef friendly fish.
Jim 8)