Moorish Idol

Geographic Origin and Biotope: Tropical Indo-Pacific (from East Africa to Hawaii). Inhabits coral lagoon reefs, reef slopes and deep wrecks (up to 180 meters / 600 ft), where it grazes on sponges among the rocks.

Taxonomy and Morphology: Moorish Idol (Zanclus cornutus). The only living species of its family (Zanclidae). Often confused with butterflyfish (Heniochus), but related to surgeonfish. High and compressed disc body, elongated snout and dorsal fin extended into a long and spectacular filament (Pennant).

Social Behavior: Hyperactive and difficult. Incessant and neurotic swimmer, never stands still. In nature it lives in small groups, but in the aquarium it is extremely intolerant towards conspecifics (they kill each other) and must be kept alone.

Coloration and Sexual Dimorphism: The Moorish Idol (Gill from "Finding Nemo"). Black vertical bands on a bright white/yellow background, with a "nose" saddled with bright neon orange. They develop two ossified "horns" above the eyes (hence "cornutus"). No dimorphism.

Aquarium Setup: Exclusive for Experts (Minimum 180 cm / 72 inches / 200G). Needs a monumental tank with huge expanses of free swimming space and rocks colonized by sponges. They suffer terribly in closed spaces and get depressed easily.

Diet and Feeding: The Feeding Challenge. Spongivore (Sponge specialist). 90% of Zanclus starve in the aquarium because they refuse any substitute food. They must be fed with frozen sponge-based pastes for Angelfish (Angelfish formula), fresh open clams and Nori seaweed, several times a day.

Water Quality: Intolerant to any fluctuation or pollutant (Pristine Water). A slight ammonia or nitrite spike leads to immediate lethargy.

Compatibility and Tankmates: Very shy at first, allows itself to be stressed by overly lively tankmates (aggressive Tangs) that would prevent it from feeding. Not Reef Safe (nips LPS corals and ornamental sponges).

Aquarium Reproduction: Totally impossible. The larvae spend a very long pelagic period developing an alien morphology before settling on the reef.

Risks and Diseases: Premature death. Fish ethically not recommended to the average hobbyist. The difficulty of weaning and the propensity to get sick with ich due to travel stress make the survival rate in the aquarium after one year frighteningly low.