Zanclus cornutus

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Latin name Zanclus cornutus
Local name Moorish Idol
Family Zanclidae - Zanclus
Origin East Indian Ocean, West Indian Ocean, Australia, Indonesia, East Pacific, Central/West Pacific
Max length 25 cm (9,8")
As aquarium fish
Minimum volume 1000 cm (264 gal)
Hardiness Delicate
Suitable for aquarium Experience, preparation and extra care required
Reef safe Reef safe with caution
Aggressiveness Docile
Recommended Microalgea (Eg. spirulina)
Macroalgea (Eg. seaweed / nori)
Mostly Other invertebrates
Beware of
Difficult to keep

It is recommended that this species be kept by experienced aquarists as it requires specialized food for its continual survival.

Subsceptible to ich

This species is easily susceptible to Marine Ich (Cryptocaryon irritants), when stressed by other fish, bad water quality, or when relocated.

Keep in mind
Frequent feeding

This species requires frequent feeding, at least a couple of times per day.

Sensitive during transportation

This species is very sensitive during transportation and acclimatizing into the aquarium.

Fastidious feeder

These fish eat exceptionally slowly and can be very selective feeders.

It can therefore be problematic to provide it with a sufficient and varied diet, in an aquarium with other, faster feeding species.

Well established aquarium with algae

These fish should be kept in a well run aquarium where they can "graze" algae from rocks and stones.

If there are insufficient algae on the rocks, it is important to feed more frequently and supplement with algae rich food e.g. Spirulina. 

Requires plenty of space for swimming.

This species revels in swimming and requires an aquarium with ample space.


This species is very shy and docile, so one should be careful when keeping it with more aggressive fish.

Descriptions and further reading
Family description (Zanclidae)

Moorish Idols (Zanclidae) have an impressive and special appearance, but are unfortunately quite difficult to keep.

A large number of these fish will die from malnutrition or because they refuse to feed. 

In the wild they survive off of sponges, but they will quickly empty the aquarium of these. If one wishes to keep these fish, it is therefore imperitive to research the different types of specialist foods beforehand, so as to be prepared and have a good feeding plan. 

This fish is particularly susceptible to diseases, which combined with their need for specialist food, makes Moorish Idols difficult to keep in a tank. 

Moorish Idols are not reef safe, as they will often eat zoanthus.

This is a very special fish, but if one wishes to avoid the challenges of keeping Moorish Idols, Heniochus diphreutes is a good alternative.

References and further reading

About references

Kenneth Wingerter. 2012. Aquarium Fish: Reconsidering the Moorish Idol - Advanced Aquarist - (English)
Bob Fenner. Tips on Helping the Moorish Idol to Survive in Captivity - Fish Channel - (English)
Bob Fenner. The Moorish Idol, Zanclus cornutus, Family Zanclidae - Wet Web Media - (English)