Moorish idol (Zanclus cornutus) care guide

Group
Marine fish
Family
Zanclidae (Moorish idol; the only living species)
Origin
Indian and Pacific Oceans, East Africa to Hawaii and Easter Island, and the eastern Pacific from the Gulf of California to Peru; lagoons and reefs at 1–180 m.
Water
saltwater
Maximum size
23 cm
Temperature
24–27°C
pH
8.1–8.4
Hardness
Salinity SG 1.023–1.026
Minimum tank
500 litres
Care level
expert
Temperament
semi_aggressive
Reef safe
with_caution

Care

Notoriously hard to keep: many imported fish refuse to feed and die. It needs a large, mature tank with lots of open swimming space (the 500-litre minimum is our estimate; sources suggest over 380 litres), excellent water quality and plenty of established live rock. Water figures given here are general marine aquarium guidance, not species-specific: 24–27 °C, pH 8.1–8.4 and salinity SG 1.023–1.026, with stable, well-oxygenated water. Usually seen in pairs or small groups; adults gather in huge schools to spawn. Heniochus butterflyfish are often suggested as an easier lookalike. The IUCN lists it as Least Concern (2015), though reef decline from climate change affects its habitat. Sources: Wikipedia, List of marine aquarium fish species (en.wikipedia.org/wiki/Listofmarineaquariumfishspecies); Wikipedia (en.wikipedia.org/wiki/Zancluscornutus). Checked October 2026.

Diet

In the wild it eats mainly sponges, plus algae, coral polyps, sea squirts and other invertebrates. In aquaria it may refuse food entirely, or eat everything at once. Try sponge-based frozen foods, mysis, chopped seafood, nori and live rock grazing, several times a day.

Breeding

Not bred in captivity. It is a pelagic spawner; eggs and larvae drift for a long time, which explains its very wide range.

Compatibility and tank mates

Reef safe only with caution: it nips sponges, coral polyps, tunicates and other sessile invertebrates. Keep with peaceful, non-competitive fish; avoid aggressive tangs that may compete for food.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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