They are uniformly blue with a yellow spot on their heads that fades as they age. They average 30 to 75 centimetres (12 to 30 in) in length with a maximum length of 1.2 metres (3 ft 11 in). They develop a large "beak" like other parrotfish that is used for scraping algae and small organisms from rocks. They have pharyngeal teeth that grind ingested rocks into sand. No other species has this uniform blue color as adults. They weigh about 9.1 kilograms (20 lb). Learn more about Blue Parrotfish