Bluespine Unicornfish (Naso unicornis)

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Bluespine Unicornfish
Naso unicornis
Bluespine Unicornfish (Naso unicornis)
Name Bluespine Unicornfish
Name Lat. Naso unicornis
Family Surgeonfishes
Family lat. Acanthuridae
Order Surgeonfishes
Order lat. Acanthuriformes
Origin Indo-Pacific
Habitat Lagoons, seaward reefs
Diet Omnivore
pH 8.1-8.4
Hardness 8-10 °KH
Behavior Semi-aggressive
Keeping Pair, group
Reef Compatible Yes
Care Level Difficult
Life Span 5-10 years
Protection No
Metric Units
Size 50 cm
Temperature 24-28 °C
Salinity 33-36 ‰
Aquarium ~ 3.500 l
US Units
Size 20"
Temperature 75-82 °F
Salinity 1.020-1.025 sg
Aquarium ~ 900 gal

Distribution and habitat

The range of Naso unicornis is the Red Sea, Indian and Pacific Oceans, from East Africa to Australia and the west coast of Central America. They mostly live in lagoons and on outer reefs with strong currents.


They require a well-structured aquarium with a lot of swimming space and a reef structure (hiding, resting and retreat possibilities) with living stones that act like a biological filter as well as fine-grained sand surfaces. Only lime-rich, heavy metal-free substrates may be used as substrate

Filters, skimmers and heaters are necessary to ensure water quality, as well as pumps to simulate tides, swells and bottom currents. Lighting must match the species-appropriate day-night rhythm of the animals

Salinity: 33-36 ‰ pH value: 8.1-8.4
Carbonate hardness: 8-10 °KH Nitrate content: 2-8 mg/l
phosphate content: 0.01-0.1 mg/l nitrite content: 0.0-0.05 mg/l

For salinity, an average value should be aimed for, which may only vary slightly by +/- 0.5 ‰. Ammonia and ammonium must not be measurable. Special attention must be paid to constantly good water quality.


They feed mainly on plankton and plant food. The feed change usually succeeds without problems. The food supply should consist of a commercially available, vitamin-enriched frozen special food mix for planktivores or a combination of live and frozen food, such as mysis, plankton, artemia and krill with chopped shrimp and mussel meat. In addition, they need plenty of commercially available algae and kelp (e.g. nori, caulerpa, kelp) supplemented with high-quality flake or granulated food for herbivores. The plant food strengthens their immune system and reduces aggression. Fine coral sand serves as a digestive aid for them

It is recommended to feed small portions several times a day (3-5 times). Regular and varied feeding promotes health and increases resistance.

Behaviour and compatibility

Since these lively and swimming fish usually live in loose groups or shoals, it is recommended to always keep several animals at the same time. To avoid ranking fights, one group should be added to the aquarium at a time. They are often aggressive against other surgeonfish, towards all other fish they behave peacefully.

Sex dimorphism

Adult males usually have a stronger horn, stronger caudal spines, and longer extended caudal fins than females of the same size.

Reproduction and breeding

There are no known reports of successful breeding in the aquarium.


They require a lot of swimming space, so a center reef setup in the aquarium that these permanent swimmers can circle is recommended

They have spines (scalps) on both sides of the caudal peduncle, which can easily get caught in the net when caught and cause painful stinging injuries when touched

As coral reef dwellers, they should not be maintained in a fish-only aquarium.

If different species are kept together, care should be taken to ensure that the fish are compatible in terms of water quality and temperature requirements and social behavior, and that the setup meets the needs of all species kept together. New fish to be introduced must be acclimated slowly to the water in the aquarium.

Further literature can be found in your pet store.


Text: Werner Winter; Image: Franz Lowak

Source: KUITER, DEBELIUS (2007): Atlas der Meeresfische: Die Fische an den Küsten der Weltmeere, Kosmos Verlag; BAENSCH & DEBELIUS (2006): Meerwasser Atlas Bd. 1, Mergus Verlag; ENGELMANN (2005): Zootierhaltung - Tiere in menschlicher Obhut: Fische, Verlag Harri Deutsch

  • Gemäß § 21 Abs. 5 Tierschutzgesetz idgF