Their numerous teeth are arranged in a tightly packed mosaic on the external surface of the jaw bones, forming a parrot-like beak which is used to scrape algae from coral and other rocky substrates.
Most of the Parrotfish I have seen have been brightly coloured in shades of blue, green, red and yellow. Although they are considered to be herbivores, parrotfish eat a wide variety of organisms that live on coral reefs and some species may include corals polyps in their diet.
Their feeding activity is important for the production and distribution of coral sands in the reef and can prevent algae from choking coral. Ingested during feeding, coral rock is ground up by their teeth. After they digest this it is excreted as sand thus at times creating small islands and the sandy beaches of the Bahamas and Caribbean.
Maximum sizes vary widely within the family, from 20 cm in the smallest species, such as the green parrotfish to 1.5 m in the largest species, the bumphead Parrotfish.
Parrotfishes are diurnal and stay within shallow waters of no more than about 70 meters in depth. By night they cram themselves into crevices, some species secreting a thick coat of mucus, like a little surrounding bubble. The mucus is thought to mask their scent from nocturnal predators such as the moray eel and may serve to protect the fish from infection by parasites.
At this point, they are fairly easy to spot when night diving and on more than one occasion, I have picked one up and placed it in Yim’s hands and motioned for her to shake it just a bit and the Parrotfish will wake up and swim away, in a bit of a dash.
What’s also interesting is that after a massive die-out of the sea urchins in the Caribbeans, parrotfish now are the main grazers in the area. While underwater, it is often easy to hear Parrotfish before you see them as you can hear them crunching the coral reef. In fact, protecting parrotfish is proposed as a way of saving Caribbean coral reefs from being overgrown with seaweed, since Parrotfish are such productive producers of sand.