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A Moorish idol is a saltwater tropical fish that commonly inhabits the shallow waters in reefs and lagoons. This fish can be found in the oceans between Australia and Hawaii, and between the western coast of Central America and the African coast. Moorish idols were given their name by the African Moors who believed that these fish bring happiness. The Moorish idol averages a length of around 7 inches (17.78 cm), with some mature specimens attaining a length of 8 - 9 inches (20.32 - 22.86 cm). These fish are often confused with bannerfish and butterflyfish, but are the only members of the Zanclidae family.
Frequently seen alone, Moorish idols occasionally swim around in pairs and sometimes form small schools, especially when young. They are a diurnal species, staying at the bottom of the lagoon or reef at night, and fading to a dull coloration. During the day, they display distinctive, vertical bands of white, black, and yellow. Their bodies are tall, round, and slim, with a long, trailing dorsal fin. The striking coloration makes them attractive to aquarists, but they usually do poorly in captivity.
If a person does decide to try keeping this colorful fish in an aquarium, the Moorish idol requires an absolute minimum of a 125 gallon tank, and a 200 gallon tank is preferred. This fish frightens easily, so the aquarium should provide plenty of cover where it can hide. Generally a peaceful fish, mature idols can become aggressive towards other members of their species, so it is recommended that only one of these fish or a mated pair be kept in an aquarium with other non-aggressive fish. At times, smaller idols will get along well in a group, but occasionally one Moorish idol in the school will become aggressive and attack the other fish. Due to the difficulties most encounter when trying to maintain Moorish idols in an aquarium, some hobbyists choose to keep fish that resemble the idols instead, such as the pennant coral fish and false Moorish idol.
In its natural habitat, the Moorish idol is an herbivore that mainly eats the algae and sponges found among coral reefs. Moorish idols kept in an aquarium are omnivores that will eat algae, small crustaceans, and finely-chopped portions of fresh and frozen marine foods such as clams, shrimp, and squid. The Moorish idol gained its popularity from the character Gill in the movie Finding Nemo, but those who subsequently tried to add this beautiful fish to their aquariums quickly learned that the Moorish idol does best among the reefs and lagoons of its tropical home.