Heniochus monoceros

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Facts
Latin name Heniochus monoceros - Cuvier, 1831
Local name Masked bannerfish
Family Chaetodontidae - Heniochus
Origin East Indian Ocean, West Indian Ocean, Australia, Japan, The Red Sea, Indonesia, East Pacific, Central/West Pacific
Max length 24 cm (9.4")
As aquarium fish
Minimum volume 600 l (158 gal)
Hardiness Average
Suitable for aquarium Suitable with care
Reef safe Not reef safe
Aggressiveness Docile
Feed
Recommended Other invertebrates
Small crustaceans (Krill, mysis, artemia...)
Zooplankton (Cyclops, pods...)
Mostly Large polyp stone coral (LPS)
Soft coral
Beware of
Eats tubeworms

This species likes to eat tubeworms.

Can nibble at clams

This species sometimes nibbles at clams including Tridacna species.

Keep in mind
Requires a varied diet

This species must be fed with an appropriately varied diet.

Acclimitises best as a juvenile

This species will better acclimatize to the aquarium`s condition if introduced, when young.

Very small individuals can be very delicate.

Frequent feeding

This fish requires feeding several times a day, especially when newly added.

When the fish can find its natural food in the aquarium it requires less frequent feeding. 

Hiding places

This species needs good hiding places, for example, between live rocks.

Requires plenty of space for swimming.

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

Docile

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

Descriptions and further reading
Genus description (Heniochus)

This species is well known for their long dorsal fin, hence the name Bannerfish.

The most interesting species of this genus are H. acuminatus and H. diphreutes, as they are the easiest to keep.
H. diphreutes, especially, is a good choice for aquarists who wish to keep Butterflyfish in a coral aquarium, as they are often reef safe if well fed.  

 

 

Family description (Chaetodontidae)

The Butterflyfish are known for their attractive patterns and colours. They are closely related to Angelfishs, but can always be distinguished, as they lack the spines on each side of the head of the Angelfish.

A smaller group of these fish will seek out primairily soft corals, like Zoanthus. A larger part of the species will target different types of LPS corals. Butterflyfish are also known to seek out anemones, tubeworms and bristleworms.

Therefore it is important to choose the correct species in relation to the corals wanted, if one desires to keep Butterflyfish in a coral-aquarium.
Bristleworms, tubeworms and other small invertebrates are also a part of the diet for many Butterflyfish.

It can be problematic, with many of these species, to get them eating in the beginning, but many of the species cannot resist live zooplankton or live mussels with crushed shells. Another option is to mimic their natural behaviour by stuffing their food into coral skeletons or stones.

They ignore most other fish and are generally peaceful, therefore multiple Butterflyfish will have no problem living together. One should however be cautious about keeping similar species together unless they are a couple.

As these fish can be difficult to acclimatize and get feeding, it is important to buy healthy fish, to avoid having to deal with more problems. Make sure to check that they do not have parasites or any visible infections.

There are some species that should not be kept in an a aquarium, as they are food specialists and will almost always refuse to eat replacement foods. It can be possible to breed some species, which will eat frozen foods. Otherwise the only way to keep food specialists is by feeding them their natural diet, which consists of live SPS or LPS corals for example.

FishBase
Aquarium trade Yes
Distribution Indo-Pacific: East Africa to the Tuamoto Islands, north to southern Japan, south to New South Wales and Tonga.
English common names Masked bannerfish
French common names Hénioche cornu
Poisson cocher masqué
Danish common names Maskevimpelfisk
References and further reading

About references

Bob Fenner. Bannerfish Butterflies, The Genus Heniochus - Wet Web Media - (English)

Scott W. Michael. 2004. Angelfishes and Butterflyfishes (Reef Fishes Series Book 3) TFH Publications / Microcosm Ltd. - (English)
Bob Fenner. Butterflyfishes; Separating the Good Ones and Those You Don't Want - Wet Web Media - (English)
Collection of links to additional information - Wet Web Media - (English)
Tea Yi Kai. 2014. Reef Nuggets 2: Aquatic Lepidopterans for your reef (Revised edition) - Reef Builders - (English)