Ocean surgeonfish
Acanthurus tractus
The Ocean surgeonfish features a vibrant blue body with a distinctive yellow tail and sharp spine on the caudal peduncle.
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About the Ocean surgeonfish
A sturdy Atlantic tang that cruises Caribbean reefs in small groups scraping algae from rocks. Look close and you can see fine radiating lines behind the eye and a pale tail base spot, plus the sharp tail "scalpel" it uses for defense. It gets big for home tanks and needs lots of swimming room and constant greens.
Also known as
Quick Facts
Size
38.1 cm SL
Temperament
Semi-aggressive
Difficulty
Intermediate
Min Tank Size
180 gallons
Lifespan
up to 32 years
Origin
Western Atlantic - Florida, Bahamas, Caribbean Sea, Gulf of Mexico to Trinidad and Tobago
Diet
Herbivore - grazes benthic algae; in aquaria feed marine algae (nori), spirulina, and herbivore pellets
Water Parameters
21-25°C
8.1-8.4
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This species needs 21-25°C in a 180 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it at least 180 gallons with a long, open swimming run; adults can hit 38.1 cm and spend the day cruising.
- Hold temperature at 21-25 C and pH at 8.1-8.4; stability beats chasing exact numbers.
- This is a true algae grazer—feed marine algae sheets (nori), spirulina, and herbivore pellets daily.
- Let some film algae grow on rocks and keep open rockwork so it can pick all day without tight turns.
- Semi-aggressive, especially toward other tangs; keep one per tank unless you have a very large system, and add it after more peaceful fish.
- Watch the tail—there is a sharp caudal scalpel, so use specimen containers instead of nets and mind your hands.
- Plan for the long haul: they can live up to 32 years.
- To confirm you have Acanthurus tractus, look for fine radiating lines behind the eye and a pale spot at the base of the tail.
Compatibility
Good Tankmates
- Large angelfish (Pomacanthus/Holacanthus) - robust, similarly sized fish that use different feeding niches; suit big, active systems
- Active, hardy wrasses (Halichoeres and Thalassoma types) - fast swimmers that ignore algae and hold their own
- Planktivorous, generally peaceful triggers (Xanthichthys spp., e.g., sargassum trigger) in large tanks
- Basslets and grammas (Gramma, Liopropoma) - small cave dwellers usually ignored by tangs
- Reef-safe butterflyfish with some size (hardier Chaetodon species like foureye or spotfin) in mature systems
- Cleaner shrimps and other reef-safe inverts (Lysmata, peppermint shrimp, snails, hermits) - generally left alone
Avoid
- Conspecifics and other Acanthurus or similarly shaped surgeonfish - high risk of tang-on-tang aggression in 180 gal
- Aggressive triggers and large predators (Balistes, Balistoides, Rhinecanthus triggers; big groupers) - may harass or injure
- Very slow or timid fish (seahorses, pipefish, mandarins) - outcompeted and stressed by a large, active surgeonfish
- Rock-grazing herbivores that compete for algae (algae blennies, rabbitfish) - often provoke territorial disputes
Ocean surgeonfish (Acanthurus tractus) is a sturdy Atlantic tang from the Caribbean and nearby waters. It cruises reefs in small groups, scraping algae from rock. Look closely and you will see fine radiating lines behind the eye, a pale spot at the base of the tail, and the sharp tail scalpel used for defense. It gets big (up to 38.1 cm SL) and can live a long time, so plan for a permanent, spacious home.
Origin and natural habitat
Western Atlantic: Florida and the Bahamas through the Caribbean Sea and Gulf of Mexico to Trinidad and Tobago. On the reef it spends the day on the move, grazing benthic algae from hard surfaces, often in small groups.
Aquarium setup and water conditions
Minimum tank size is 180 US gallons. Give it long, open swimming space with rockwork that offers broad surfaces for algal films to grow and be grazed. Keep stable marine conditions within 21-25 C and pH 8.1-8.4. This is a large, active fish; cramped layouts and narrow tanks make it restless and more combative.
Let some green film algae develop on parts of the rockwork and back glass. Scrape viewing panes as needed, but leave safe grazing areas for the fish.
Handle with care. The tail "scalpel" is sharp and can cut. Use containers or soft nets and avoid bare-hand captures.
Diet and feeding
Herbivore. In the wild it grazes benthic algae throughout the day, so provide constant greens in the aquarium. Offer marine algae and plant-based prepared foods and encourage natural algal growth on rock.
- Dried seaweed (nori) on a clip
- Spirulina-based flakes or pellets
- Formulated herbivore pellets or wafers
- Access to natural algal films on live rock
Behaviour and tankmates
Semi-aggressive. Generally peaceful toward dissimilar fishes but will defend space and may spar with other surgeonfishes, especially similar-shaped species. In community systems, give it plenty of room and avoid keeping it with closely related tangs unless the tank is very large. Adequate swimming space and regular feeding go a long way toward keeping the peace.
Common problems and how to avoid them
Most issues trace back to size, diet, and stability. A fish this active becomes stressed and combative in undersized tanks, and poor nutrition shows quickly in body condition.
- Start with a 180+ gallon tank and open swimming lanes to reduce pacing and aggression.
- Feed algae daily (nori, spirulina, herbivore pellets) and allow grazeable surfaces.
- Keep water stable within 21-25 C and pH 8.1-8.4.
- Quarantine new arrivals and maintain good husbandry to limit disease introduction.
- Avoid crowding with other tangs unless the system is very large.
Documented lifespan reaches up to 32 years. This is a long-term commitment.
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