I think the tank will be cramped with one. IMO it is close to pushing it in terms of number of fish.
Parrotfish get very large, and their diet, as mentioned, is TOTALLY different than other aggressive fish. Many aquaria make feeding blocks for them basically with plaster, algae sheets/wafers so that they can grind on things and still get algae. They do, by nature, basically take bites out of coral/rock.
IMO, it is not a good combination.