Moorish idol

Care at a glance

Overview

The Moorish idol is a peaceful reef fish, widely considered the hardest commonly sold marine fish to keep alive. Most hobbyists, even experienced ones, are better off enjoying it on the reef or at a public aquarium.

Caring for the Moorish idol

A Moorish idol needs a long, open tank of at least 125 gal (473 L). Fill it with mature live rock carrying a real growth of sponges and algae. That natural food source matters more to its survival than almost anything else in the setup. Keep the water at 72 to 79°F (22 to 26°C) with a pH of 8.1 to 8.4.

Roughly 80 to 90 percent of imported Moorish idols die within their first year, most within the first month. Almost always, the cause is that they refuse to eat in captivity. Have a long list of foods on hand before the fish ever arrives.

Moorish idols are peaceful, almost timid fish that rarely bother tank mates, and they are fine alone or in a group. They graze on coral polyps and zoanthids, so they are reef safe only with caution.

Good to know

Zanclus cornutus is the only species in its family, Zanclidae. Its long, sickle-shaped dorsal fin and small, bristly-toothed snout set it apart from surgeonfish and butterflyfish. The snout is built for picking food out of tight crevices. In the wild, sponges make up roughly 70 percent of its diet, rounded out with algae, tunicates and small amounts of coral polyps. Its larvae drift in the open ocean for around 70 days before settling on a reef. That unusually long pelagic stage explains how the species spread so widely across the Pacific and Indian Oceans.

In the wild

Moorish idols range across nearly the entire Indo-Pacific, from East Africa and the Red Sea to Hawaii and Easter Island. An isolated population also lives in the eastern Pacific, from the Gulf of California to Peru. They live on reef flats and seaward reefs, usually alone, in pairs or in small groups of two or three. They occasionally gather into much larger aggregations to spawn.

Common questions

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