Horse-face unicornfish
Naso fageni
Naso fageni is a large Indo-Pacific surgeonfish characterized by its unique horse-like head profile. It requires an exceptionally large aquarium to accommodate its adult size.
Water Temperature
24 - 28 °C
pH Value
8.1 - 8.4
Water type
Marine
Tank level
Middle
Adult size
80 cm
Minimum tank volume
>= 1,800 L
Minimum group
>= 1
KH
8 - 12 dKH
Species description
Geographical Origin and Habitat:
This species is widely distributed across the tropical waters of the Indo-West Pacific, ranging from the eastern coasts of Africa (including Kenya and Tanzania) to the Philippines, and north to southern Japan. It primarily inhabits deep outer reef slopes, coastal rocky reefs, and current-swept channels at depths between 3 and 40 meters, often observed swimming in open waters above coral structures.
Taxonomy and Morphology:
Belonging to the family Acanthuridae and the genus Naso, Naso fageni is characterized by a unique horse-like head profile with an elongated snout and a straight or slightly concave forehead. It does not develop a protruding bony horn. Adults can reach an impressive size of 60-80 centimeters. It features two sharp, fixed plates (scalpels) on each side of the caudal peduncle.
Social Behavior:
An active, schooling species that forms small groups or large mobile shoals in the wild to forage along reef slopes. In the aquarium, it requires massive amounts of open water to swim. It is generally peaceful toward smaller, non-related tankmates but can exhibit territorial behavior toward conspecifics or other Naso species.
Coloration and Sexual Dimorphism:
The base body color is a uniform grayish-brown to light olive-green, fading to pale white on the belly. It lacks the complex color patterns of other Naso species. Mature males develop very long caudal filaments on the tips of their lyre-shaped tail and may have larger caudal plates than females.
Care, breeding and tankmates
Aquarium Setup:
Requires a massive marine aquarium of at least 1000-1200 liters due to its large size and active swimming behavior. The aquascape should be minimal and kept to the back and sides to maximize open swimming space. Powerful circulation pumps are required to create strong water movement and maintain high oxygen levels.
Diet and Feeding:
Primarily herbivorous, feeding on benthic macroalgae. In captivity, it must be fed multiple times per day with dried nori sheets, spirulina, and high-quality vegetable-based flakes or pellets. Supplement occasionally with frozen foods like mysis and krill to support its high metabolic rate and prevent weight loss.
Water Quality:
Demands pristine and stable water parameters: temperature between 24°C and 26°C, pH from 8.1 to 8.4, specific gravity (SG) from 1.020 to 1.025, and carbonate hardness (KH) of 8 to 12 dKH. Strong surface agitation is essential to maintain high oxygenation. A heavy-duty protein skimmer is mandatory to handle waste.
Compatibility and Cohabitation:
Peaceful toward smaller reef fish and completely reef safe regarding corals. However, large specimens can easily knock over unsecured rockwork or corals when swimming quickly. It houses well with other non-aggressive tangs, angelfish, and wrasses. Avoid keeping more than one specimen of this species per tank.
Aquarium Breeding:
Captive breeding in home aquariums is not documented and is considered impossible due to the immense swimming space required for their pelagic spawning rituals. In nature, pairs rise rapidly toward the surface at dusk to release gametes into the water column. The pelagic eggs hatch into delicate larvae that drift with ocean currents.
Risks and Diseases:
Prone to Head and Lateral Line Erosion (HLLE) if fed an inadequate diet or exposed to poor water conditions. It is also highly susceptible to external marine parasites like Cryptocaryon irritans (marine ich). A strict quarantine process and the use of a UV sterilizer in the filtration system are highly advised.
Geographic Origin and Distribution
This species is widely distributed across the tropical waters of the Indo-West Pacific, ranging from the eastern coasts of Africa (including Kenya and Tanzania) to the Philippines, and north to southern Japan. It primarily inhabits deep outer reef slopes, coastal rocky reefs, and current-swept channels at depths between 3 and 40 meters, often observed swimming in open waters above coral structures.
Origin
Tropical oceans and reefsNorth AmericaAfrica and MadagascarSouth and Southeast AsiaEast Asia
Fish profile
- Temperament
- Peaceful
- The Naso fageni boasts a gentle giant temperament, being largely peaceful and highly personable with its human caretakers. Once acclimated, they often recognize their owners and will readily eat right from the aquarist's hand. They do not bother corals, invertebrates, or smaller fish, making them a centerpiece for giant reef tanks. Aggression is typically only displayed towards other large tangs or if they feel confined in a tank that is too small. Overall, they are majestic, calm, and highly rewarding fish for those with adequately sized systems.
- Diet
- Herbivore
- The Naso fageni is primarily herbivorous, requiring a diet exceptionally rich in marine algae to thrive long-term. Dried nori or sea veggies should be offered daily, secured to a rock or a veggie clip for continuous grazing. They will also eagerly accept meaty offerings like mysis shrimp and krill, but meat should only make up a small portion of their diet. Providing spirulina-enriched flakes and pellets ensures they receive proper vitamins. A varied, algae-heavy diet prevents nutritional deficiencies and helps maintain their immune system.
- Life expectancy
- 15-20 years
- It has a very long lifespan, estimated between 15 and 20 years under proper husbandry conditions. To reach this age, it requires exceptional water quality with oversized filtration and constant water changes to prevent nitrate accumulation. Immense swimming space and a stress-free environment are essential to ensure its longevity.
- Adult size
- 80 cm
- The catalog's scalar value is 80 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 80 cm for this species, recorded as fork length (FL). The taxonomic record consulted is Naso fageni (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Solitary
- Sexing the Naso fageni is possible as they reach maturity, though it depends heavily on the specific species within the genus. Males often develop much larger and more prominent rostral horns or facial features compared to females. Furthermore, adult males may display elongated tail streamers (lyretails) which are absent or much shorter in females. Despite these differences, sexing is largely irrelevant for home aquarists since they are not bred in captivity. Keeping a single specimen or a known pair requires an enormous aquarium either way.
- Feeding frequency
- Twice daily
- Because of their constant grazing habits in the wild, the Naso fageni needs to be fed multiple times per day. Having nori constantly available on a grazing clip is highly recommended to satisfy their instinct to forage. In addition to constant grazing, they should be offered prepared foods two to three times daily. This heavy feeding schedule is crucial to maintain their body weight and overall health. A well-fed Naso tang is more robust, less aggressive, and more resistant to common parasites like Cryptocaryon irritans.
- Bioload
- The Naso fageni produces a massive bioload due to its large adult size and voracious herbivorous appetite. They consume massive amounts of plant matter and excrete proportionally large amounts of waste. A heavy-duty protein skimmer, mechanical filtration, and possibly a biological reactor are required to process their waste. Keeping water parameters pristine is essential, as large tangs are susceptible to lateral line disease if water quality degrades. Regular, high-volume water changes are an absolute necessity when housing this majestic fish.
- Flow
- Strong
- The Naso fageni requires extremely strong, turbulent water flow to simulate the highly oxygenated reef drop-offs they inhabit in nature. They are incredibly strong swimmers and rely on heavy currents for exercise and proper respiration. Utilizing multiple high-capacity wavemakers or gyre pumps is necessary to keep water circulating aggressively. High flow also aids in keeping detritus suspended so the heavy filtration can remove it. Proper oxygenation driven by this flow is critical for their fast metabolism.
- Jump risk
- Yes
- Large and powerful, the Naso fageni possesses a significant jump risk, especially during their initial acclimation period or if startled at night. Their sheer size and muscle mass mean they can easily launch themselves out of open-top aquariums. A sturdy, tightly fitted mesh cover is absolutely mandatory to prevent these expensive and beautiful fish from ending up on the floor. Heavy glass or acrylic lids can be used, but mesh is preferred to allow for maximum gas exchange. Minimizing sudden movements outside the tank also helps keep them calm.
- Reproduction
- Oviparous
- The Naso fageni has not been successfully bred and reared in the home aquarium due to the complex requirements of their pelagic larvae. In the ocean, they participate in mass broadcast spawning events, releasing millions of eggs into the water column. The larvae undergo an extended pelagic phase before settling onto the reef as juveniles. Mimicking the physical space and specific dietary needs of the larvae is currently beyond the capabilities of standard captive environments. Therefore, all specimens in the trade are wild-caught.
- Compatibility & tankmates
- Peaceful
- Generally, the Naso fageni is very peaceful toward completely different species and makes a fantastic addition to a large community reef aquarium. They are entirely reef safe and will actively graze on nuisance algae without bothering corals or motile invertebrates. However, they can show significant aggression toward other tangs, particularly those of the same genus or with a similar body shape. If keeping multiple surgeonfish, it is best to introduce them simultaneously into an oversized aquarium. They ignore smaller fish and peaceful tank mates completely.
- Tank level
- Middle
- An exceptionally large aquarium is absolutely mandatory for the Naso fageni, with 200 gallons being the bare minimum for juveniles and 300+ gallons for adults. They are incredibly active and require massive, unobstructed swimming lanes spanning the entire length of the tank. The aquascape should be minimalist, utilizing island structures to maximize open water space while still providing large sleeping caves. Keeping them in cramped conditions causes severe stress, stunted growth, and behavioral issues. Providing adequate swimming room is the most critical aspect of their care.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 2.2 ± 0.1 se
- Resilience
- Low (4.5 - 14 years)
- Phylogenetic uniqueness (PD50)
- 0.5
- Bayesian Length-Weight
- a = 0.02089, b = 2.95
- VulnerabilityHigh vulnerability (56 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
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