Humpback unicornfish
Naso brachycentron
Humpback unicornfish feature a prominent, horn-like nasal extension and a vibrant blue-green body, with distinct yellow accents on the tail.
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About the Humpback unicornfish
A big Indo-Pacific unicornfish with a distinct humped back and, in adult males, a long horn that gives it a prehistoric look. It cruises reef slopes in small groups grazing algae all day and can grow to truly massive sizes, so it is a fish for huge marine systems only.
Also known as
Quick Facts
Size
90 cm FL
Temperament
Semi-aggressive
Difficulty
Advanced
Min Tank Size
300 gallons
Lifespan
up to 31 years
Origin
Indo-Pacific
Diet
Herbivore - grazes benthic algae; offer marine algae/nori, spirulina, and vegetable-based pellets with occasional meaty foods
Water Parameters
25-28°C
8.1-8.4
Need a heater for this species?
This species needs 25-28°C in a 300 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- This fish gets huge (up to 90 cm FL) and belongs in a true monster tank; plan for 300+ gallons with long, open swimming space.
- Hold temperature at 25-28 C and pH at 8.1-8.4, and keep those values steady.
- Feed like a grazer: offer marine algae/nori and spirulina or vegetable-based pellets daily, with meaty foods only as occasional treats; a mature tank with benthic algae to pick at helps.
- Semi-aggressive and pushy with similar algae grazers; in most setups keep it as the only large tang/unicornfish and add it late in the stocking order.
- It cruises reef slopes in small groups in the wild, but in captivity multiple specimens or similar-shaped tangs usually fight unless the system is truly enormous.
- This is a decades-long commitment: lifespan can reach 31 years, and juveniles grow into very large adults, so buy with the adult-sized system already running.
- Captive breeding for Naso brachycentron is not documented; do not expect to sex, pair, or breed it in aquaria.
Compatibility
Good Tankmates
- Large, robust angelfish that are assertive but not hyper-aggressive (Genicanthus, many Pomacanthus/Holacanthus) - similar pace and able to hold their own in big systems
- Rabbitfish/foxfaces (Siganus/Lo) - fast herbivores with a different body shape; generally coexist and help with algae control
- Schooling planktivores like anthias and chromis - occupy the water column and are usually ignored by a grazing unicornfish
- Reef-safe to moderately assertive wrasses that are fast swimmers (Halichoeres, Cirrhilabrus, Paracheilinus, Anampses)
- Robust butterflyfish (Chaetodon, Heniochus) that are not delicate - similar open-water behavior and speed
- Generally non-nippy triggers like bluejaw and sargassum (Xanthichthys spp.) or pinktail - open-water swimmers that do not harass
Avoid
- Other unicornfish or similarly shaped/diet-overlapping tangs (other Naso, many Acanthurus, large Zebrasoma) - often triggers territorial aggression
- Highly aggressive or nippy triggers and large puffers (clown, queen, undulate triggers; nippy porcupine/dogface) - likely to tail-bite or harass
- Large ambush or biting predators (big groupers, snappers, large morays) - can injure or chronically stress a roaming grazer
- Very slow or delicate species that get outcompeted by a constant cruiser and strong flow (seahorses, pipefish, mandarins)
The Humpback unicornfish (Naso brachycentron) is a striking, very large Indo-Pacific surgeonfish. Adults develop a steeply humped back and, in males, a long forehead horn that gives the species a prehistoric look. It is a constant algae grazer on reef slopes and grows to truly massive size - up to about 90 cm fork length - so it is a fish for huge marine systems only. Care is advanced, temperament is semi-aggressive, and lifespan can reach three decades.
This species needs an aquarium of at least 300 US gallons with wide open swimming space. Do not buy one for a smaller tank expecting to upgrade later - they grow and roam.
Origin and natural habitat
Indo-Pacific reef slopes and outer reefs. Humpback unicornfish cruise in small groups over current-swept zones, grazing benthic algae throughout the day. They spend much of their time in open water above hard substrate rather than weaving through tight coral thickets.
Aquarium setup and water conditions
Think in terms of a public-aquarium style layout: long, unobstructed lanes for cruising with sturdy rockwork that offers broad surfaces for algal growth. Leave plenty of open water; this is a swimmer first and a rock-dasher second.
- Minimum tank size: 300 US gallons
- Temperature: 25-28 C
- pH: 8.1-8.4
- Marine, reef-stable water chemistry
Plan for heavy filtration and strong circulation to keep oxygenation high and detritus moving. Provide continuous grazing opportunities by allowing natural film algae to establish on some surfaces. Use large tubs or boxes for handling rather than nets - like other surgeonfishes, they have sharp caudal spines that can snag or cut.
Diet and feeding
Herbivore that grazes all day. Offer varied marine greens with frequent, small feedings. Occasional meaty items are fine but should not dominate the diet.
- Dried marine algae sheets/nori clipped in multiple spots
- Spirulina-based flakes and pellets
- Vegetable-based pellets formulated for marine herbivores
- Occasional treats: mysis, finely chopped seafood
Multiple algae clips spaced around the tank reduce squabbling and encourage the natural cruise-and-graze routine.
Behaviour and tankmates
Semi-aggressive, especially toward similar-shaped algae grazers. In the wild they cruise in small groups, but the space required to keep a group humanely is beyond most home systems. Keep one per tank. Choose robust companions that do not compete heavily for algae and that appreciate ample swimming room.
- Avoid housing with other unicornfish or large tangs that share body shape and diet
- Introduce to a spacious, established tank to reduce territorial flashes
- Give line-of-sight breaks so chased fish can get out of view
Common problems and how to avoid them
- Outgrowing the tank: start with a system at or above 300 gallons and a layout that prioritizes open water
- Underfeeding herbivores: provide daily algae sheets and frequent green-based feeds to maintain weight
- Head and lateral line erosion (HLLE): linked to poor diet and water quality in surgeonfish - vary foods, keep water very clean, and avoid prolonged use of carbon dusting the water
- Aggression toward similar fish: skip redundant tangs and spread feeding stations
- Handling injuries: use containers, not nets, to avoid damage from the caudal spines
Documented lifespan is up to 31 years. Take a long-view approach to space, filtration capacity, and feeding routine.
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