Munch, munch. The queen parrotfish (Scarus vetula) scrapes algae from Caribbean coral reefs with its parrot-like beak. While feeding, hard stone and coral inevitably get mixed into its lunch, which in turn gets ground up by the fish and deposited back into the ecosystem as sand. This fish is an adult male. But when young, parrotfish have the ability to change sex, depending on the population’s needs.