I did own a parrot fish. I really loved it. The one we had seemed so docile.
I'm not sure how they get once they are older. Ours was a juvenile. We had it for about six months
My boys did not like the little guy because he was not mean and they thought he looked funny, haha. They thought he looked like a little bath tub squeaky toy, haha.

My parrot fish disappeared for two months. Even when we cleaned the tank..(which we do weekly or every 2 weeks) we could not find him. Finally, he mozied on out, but not looking that great. We are pretty sure our Devil fish had him hemmed up inside the rock cave all this time. As soon as he came out, I yelled out.. Look! My parrot is back. Diablo came in at the poor thing like a torpedo, and .. well.. guess you can figure out the rest of this story. I suppose Devil Fish need a tank of their own.

So.. having said all that, I'm a fan of the parrot..but -- for certain, research it, and see what type of fish they mingle well with and who their predators are too.