The Brown Surgeonfish is the smallest and least colorful of its genus, but makes up for this by its more peaceful demeanor with other tank mates!

   The Brown Surgeonfish or Lavender Tang, Acanthurus nigrofuscus, is brown with fine bluish gray horizontal lines on the body.  Both the dorsal fin and anal fins are brownish orange with a pale blue on the outer edges.  The dorsal fin has a black spot towards the back near the tailfin and the anal fin as a slightly smaller black spot towards the back near the tailfin as well. The tailfin is pale with a ‘V’ shaped brighter brownish orange accented upper and lower edging that has streamers.  The eye area has a pale upper blue “eyeshadow” and the lips are darker.  Their caudal peduncle area has their embedded retractable scalpel, which is surrounded black, looking like a black “dash.”   When angry, their dorsal fin will turn an intense yellow.  These smaller tangs only grow to 8.25″ (21 cm), with tangs growing to 80% of their total length within the first 4 to 5 years.  Tangs have a life span of 30 to 45 years (Choat and Axe 1996).  These tangs are great for beginners.

  Although in the wild they are seen with Convict Tangs, these are usually juveniles and they are just “users.”   Once they are adults, one Brown Surgeonfish will attempt to drive off a school of Convict Tangs as has been observed in O’ahu.  Due to the very docile nature, housing them with others in their genus will result in them being picked on, of course with the exception of the Convict Tang who they will attack.

  The Brown Surgeonfish will be quite hardy once it gets settled.  The are easy to care for, but they need to have a good macro algae cxrop, so the tank needs to be mature for the best chance of success.  Being a voracious algae eater, good algae growth in the aquarium also helps provide for its nutritional needs as well as making it an excellent candidate for a reef environment.  As most tang lovers tend to want more than one, keeping in mind it’s docile nature when choosing companions.  

  This fish, along with its close relative the Convict Tang A. triostegus, is one of the more peaceful surgeonfish, however they should not be housed together.  Others from it’s genus should be left out of the grouping unless the tank is hundreds of gallons.  Its moderate behavior makes it a good companion in a community tank. It should not be housed with aggressive species but rather more peaceful fish. It can be kept with a variety of tank mates including some of the other genus’ of surgeonfish, though it will be aggressive towards others of its own kind.

  Due to its relatively small size, the Brown Surgeonfish or Lavender Tang is a good choice for the home aquarium, requiring only 125 gallons, which is smaller than what is need for most tangs.  The Brown Surgeonfish likes a lot of water movement rather than a placid aquarium.   A quick and agile swimmer, the tank should be at least 6 feet long because it needs plenty of swimming space,.  They will enjoy corals/ rocks with crevices for retreat and for sleeping in at night. 

For more Information on keeping marine fish see:
Guide to a Happy, Healthy Marine Aquarium

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Perciformes
  • Family: Acanthuridae
  • Genus: Acanthurus
  • Species: nigrofuscus
Brown surgeonfish – Quick Aquarium Care
  • Aquarist Experience Level: Beginner
  • Aquarium Hardiness: Very Hardy
  • Minimum Tank Size: 125 gal (473 L)
  • Size of fish – inches: 8.3 inches (20.96 cm)
  • Temperament: Semi-aggressive
  • Temperature: 72.0 to 78.0° F (22.2 to 25.6&deg C)
  • Range ph: 8.1-8.4
  • Diet Type: Herbivore
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Habitat: Distribution / Background

  The Brown Surgeonfish or Lavender Tang, Acanthurus nigrofuscus, was described by Forsskal in 1775. Their most common names describe their variations in coloring and they are Blackspot Surgeonfish, Brown Surgeonfish, Dusky Surgeonfish, Lavender Tang, Spot-Cheeked Surgeonfish, and Surgeonfish.  

  Brown Surgeonfish are found in the Indo-Pacific in the Red Sea, Transkei, South Africa, Tuamoto and Hawaiian Islands.  They are also found in southern Japan, the southern part of the Great Barrier Reef, New Caledonia and Rapa.  The areas they inhabit are shallow lagoons with hard substrates and seaward reefs in deeper waters, feeding on filamentous algae.  Juveniles are initially quite wary, hiding in crevices among rubble and rocks, but soon the need for feeding draws them into small mixed groups. Juveniles, seeking protection in numbers, will join groups that consist of surgeonfish and various other like sized fish that will feed on the bottom and roam the edges of shallow reefs.  As they get older, they will join their own species to feed. 
   They are rarely seen alone or in pairs, rather they are usually found in groups. Adults are found in small groups unless they are in oceanic areas, then they will form large schools for protection.  Along with the with Convict Tang A. triostegus they are often a less aggressive surgeonfish, so are on the bottom of the pecking order. The protection of large schools allows them to invade the territories of other herbivores to feed. They sometimes can be seen grazing with a group of Convict Tangs.  Whether they are territorial or not depends on the location.    In their natural habitat they are found at depths down to about 65 feet (20 meters) feeding on benthic algae and weeds and phytoplankton. 

   They are on the IUCN Red List for Endangered Species under Least Concern.

  • Scientific Name: Acanthurus nigrofuscus
  • Social Grouping: Groups – In captivity, solitary unless tank is hundreds of gallons.
  • IUCN Red List: LC – Least Concern


  The Brown Surgeonfish or Lavender Surgeonfish has a disk like shaped body, very similar looking to other Acanthurus species. Though it is the smallest and least colorful species in this genus, it is easily distinguishable by the dull orange spots on the head and the two dark spots at the rear base of the dorsal and anal fins. Its adult coloration varies from a brown to a light grayish brown with a lavender tinge, especially on the fins. When displaying aggression its upper back and the entire dorsal fin lighten, sometimes becoming distinctly yellow.

   It has blackish brown lips, its pale pectoral fins are narrowly edged in black, and sometimes the anal fin is narrowly edged with white. Its caudal fin is lunate (crescent-shaped). On each side of the caudal peduncle is a single spine or “scalpel” used for defense or dominance. When not in use the spine is folded down into a groove that is circled in black. Caution needs to be exercised when handling surgeonfish as a cut from its scalpel can cause discoloration and swelling of the skin with a high risk of infection. The pain lasts for hours then still ends up having a dull ache.   Juveniles are brown to bluish black and have orange scribbles on the head that break up into spots as they mature.  Females are larger and they reach 8.25” (21 cm), and will live 30 to 45 years (Choat and Axe 1996), possibly less in captivity.

  • Size of fish – inches: 8.3 inches (20.96 cm)
  • Lifespan: 30 years – 30 to 45 years (Choat and Axe 1996), possibly less in captivity.

Fish Keeping Difficulty

  These small size of the Brown Surgeonfish are easy to care fore and lends itself to being a great addition to the marine aquarium. They thrive well in tanks with algae growth, and are easy to keep as long as there is plenty of this natural food.  Babies under 2″ will starve quickly without this abundance of natural greenery. It is generally quite hardy and can handle a wide range of water parameters. However it will do best in an environment that provides consistency, not only in water conditions and quality, but also in decor and fellow inhabitants. It can be housed in a fish only tank or in a reef environment as it will not harm corals or invertebrates.

  Surgeonfish and tangs are continuous feeders and they need to be provided a proper diet. They are susceptible to nutritional disorders which may cause color loss and LLD (lateral line disease).  They are also susceptible to bacteria resulting from organic buildup which deteriorates water quality. Consequently they will need vigorous filtration, protein skimming, and regular small water changes.  Not producing as much body slime, these “dry” skinned fish are more susceptible to marine velvet and crypt.

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Beginner

Foods and Feeding

   The Brown Surgeonfish or Lavender Tang are primarily herbivores. In the wild they feed almost exclusively on filamentous algae which they scrape from hard surfaces. In the aquarium the majority of their intake will be vegetable matter, but they do need some meaty foods as well. Provide lots of marine algae, prepared frozen formulas containing algae or spirulina, frozen brine and mysid shrimp, and flake foods. Japanese Nori or other seaweed can be adhered to the aquarium glass with a vegetable clip. An occasional live rock with micro and macro organisms will be greatly appreciated. Culturing macro algae like chaetomorphia in the tank is also a great idea. Feed 2 to 3 times a day in smaller amounts instead of a large quantity once a day. As continuous grazers, they will benefit from this and it will also keep the water quality higher over a longer period of time.
   Providing a vitamin supplement (including vitamin C) can help provide for their nutritional needs, and vitamin C can help prevent or reduce Lateral Line Erosion (LLE). This can be done by soaking dried pellets with liquid vitamins, adding vitamins to the food, or adding a liquid vitamin into the water. It is also said that pellets soaked in garlic may help fend off Marine Ich. Some hobbyists also report success with supplemental foods such as previously boiled or frozen zucchini, broccoli, spinach, and leaf lettuce.

  • Diet Type: Herbivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet – As a treat.
  • Vegetable Food: All of Diet – 95%
  • Meaty Food: Some of Diet – 5%
  • Feeding Frequency: Several feedings per day – At least 3 times per day with algae sheets being available throughout the day. Remove at night.

Aquarium Care

Reef tanks:
-Large Tanks 100 gallons and over, once water is aged and stable can be changed 10% bi-weekly to 20% monthly, depending on bioload.

Fish only tanks:*
-Large Tanks 100 gallons and over, once water is aged and stable can be changed 20% to 30% every 6 weeks depending on bioload.

For more information on maintaining a saltwater aquarium see: Saltwater Aquarium Basics: Maintenance. A reef tank will require specialized filtration and lighting equipment. Regular water changes done  bi-weekly will help replace the trace elements that the fish and corals use up.  Learn more about reef keeping see: Mini Reef Aquarium Basics.

*Note:  If this is the ONLY fish in the tank, with no corals or other fish you can get away 20% monthly.

  • Water Changes: Bi-weekly

Aquarium Setup

  All surgeonfish/ tangs are quick agile swimmers and need lots of open areas and the Brown Surgeonfish needs a minimum tank size of 125 gallons for adults, which should be 6 feet long. To feel secure they also need rocks/ corals with many nooks and crannies to hide in and to wedge themselves into at night for sleeping. Provide plenty of space at the upper levels and lots of rocks/ corals with crevices for retreating and for sleeping below. This decor will also lend itself to algae growth which surgeonfish enjoy grazing on, making them a valuable addition to a reef environment.  It nature it is found in sunlit areas, feeding on algae, so adding enough light to grow their algae is recommended.  The Brown Surgeonfish can also be kept under very bright light as long as some dimly lit spaces are provided.  The temperature they prefer is 72 to 79˚F (22 to 26˚C), with the lower spectrum of this range providing more oxygen.  They thrive in normal ocean salinity of 1.023 and 1.205, with a pH that is 8.1 to 8.4.  All of these parameters should be stable and should not fluctuate.   All surgeonfish need an aquarium with plenty of aeration, a strong current will help to provide good oxygenation.  This good water movement, provides them with their favorite thing, having water rush over their gills as they swim against the powerhead.  Tangs will spend time in the open water and darting in and out of the rocks/ corals. It will sleep in crevices at night, occupying all areas of the tang.  

  • Minimum Tank Size: 125 gal (473 L) – Tank should be at least 6 feet long.
  • Suitable for Nano Tank: No
  • Live Rock Requirement: Typical Plus Hiding Places
  • Substrate Type: Any
  • Lighting Needs: Moderate – normal lighting – Enough to produce algae growth
  • Temperature: 72.0 to 78.0° F (22.2 to 25.6&deg C)
  • Breeding Temperature: – unknown
  • Specific gravity: 1.023-1.025 SG
  • Range ph: 8.1-8.4
  • Brackish: No
  • Water Movement: Strong
  • Water Region: All

Social Behaviors

  Although they are peaceful to non-tang fish, they are aggressive toward others of their own species and should not be housed together.  Even though they school in the wild, in captivity, their ability to understand they are confined and have a limited territory will bring out aggression toward their own.  If attempting more than one of this genus, you will need a tank with hundreds of gallons to ward off aggression due to territorial behaviors.

  Add your Brown Surgeonfish first if they will be kept with other tangs from other genus who are larger or more aggressive. It is best to initially introduce several species together as juveniles, rather than adding a new one later on, however, choose tangs from different genus and different color and shape.  As far as adding other tangs into the tank, if there is already a resident tang, this usually poses a territory problem, which can be helped by rearranging rock work . Though a large aquarium can help alleviate many problems, be aware of the social behaviors of any species you are considering to prevent compatibility problems.  Avoid lionfish and groupers as tank mates since they will eat them due to their smaller size.  When the tank is too small, they will become more aggressive towards other fish that they wouldn’t typically bother, especially other herbivores.  In the correct sized tank, Brown Surgeonfish can also be kept in a fish only community tank with peaceful tank mates or a reef tank. This fish is very peaceful and gets along with most fish.

   The great thing about the Brown Surgeonfish or Lavender Tang is that they are fine in a reef setting with inverts and corals, making it highly useful in a reef environment. However keep corals glued down, as their quick speeds may topple a coral or two.  Corals from the LPS family are said to possibly be in danger of nipping, however a well fed tang will not even give a second glance to a coral.  They may eat the algae at the stoney base, however this should not be interpreted as “eating” the coral.

   Inverts are safe.  There has been a rare report here and there where a tang decided that the mucus of a clam was yummy and slurping it up caused the clam to stay closed and die.   This is so uncommon it is not even worth mentioning, yet it is worth mentioning since it can happen to underfed tangs.   

  • Venomous: No
  • Temperament: Semi-aggressive – Peaceful to all other non-tangs when housed in 125 gallon tank.
  • Compatible with:
    • Same species – conspecifics: Sometimes – Only if the tank is hundreds of gallons and they are added at the same time as juveniles.
    • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Safe
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Safe
    • Safe
    • Large Semi-Aggressive (tangs, large angels, large wrasses): Safe – In minimum tank size, they should be the only tang. Only tangs from other genus in hundreds of gallons.
    • Large Aggressive, Predatory (lionfish, groupers, soapfish): Threat – They will be eaten.
    • Monitor – Seahorses and most pipefish need their own tank. Mandarins will not be bothered.
    • Anemones: Safe
    • Mushroom Anemones – Corallimorphs: Safe
    • LPS corals: Safe – Tangs that are not well fed may sample this coral.
    • SPS corals: Safe
    • Gorgonians, Sea Fans: Safe
    • Leather Corals: Safe
    • Soft Corals (xenias, tree corals): Safe
    • Star Polyps, Organ Pipe Coral: Safe
    • Zoanthids – Button Polyps, Sea Mats: Safe
    • Sponges, Tunicates: Safe
    • Shrimps, Crabs, Snails: Safe
    • Starfish: Safe
    • Feather Dusters, Bristle Worms, Flatworms: Safe
    • Clams, Scallops, Oysters: – A very RARE tang will find the slime clams produce yummy, causing the clam to close and stress.
    • Copepods, Amphipods, Mini Brittle Stars: Safe

Sex: Sexual differences

Like other Acanthurus, males may be much smaller than females.

Breeding / Reproduction

   The Brown Surgeonfish, unlike other genus of the tang/surgeon family, the females of the genus Acanthurus are larger than males.  They are open water spawners and form pairs.  These pairs seem to stay together even within groups.  The male may exhibit color changes during spawning to attract female and to warn rival males.  If they are in a large school, a pair will break away and rise upward toward the surface and release their gametes. These little floating fertilized eggs are spherical and have a single oil globule to aid in their buoyancy and dispersal.  Each egg measures around 0.17 mm in diameter.   Once they hatch, the larvae look like little kites with a long snout with a small mouth, and they stay in this state for 42 to 68 days.  During this time, they fall prey to fish and other marine animals.  Once they reach around 1 inch, give or take (23 to 33 mm), the  larvae are then changed into the juvenile stage.  Once they are ready to join the reef, the larvae settle out of the water column and develop into these 1” juveniles, seeking the protection and food sources of the reef and seagrass habitats. 

   Some species of surgeonfish have spawned in public aquariums and there have been a few scattered reports of spawning in home aquariums, but regular spawning and the rearing of the young has not yet been reported.  Though the Brown Surgeonfish has not yet been bred in captivity,

   For information on breeding and the development of the fry, see: Marine Fish Breeding: Tangs.

  • Ease of Breeding: Unknown

Fish Diseases

   Tangs produce less body slime than other saltwater fish and have been termed “dry skinned” fish by some.  This makes them very susceptible to Cryptocaryon (saltwater ich) and other diseases.  The most common ailments are bacterial diseases, Hole-in-the-Head Disease, Lateral Line Disease, and parasitic infections such as protozoas (including Cryptocaryon), worms, etc.  

   For Crypt, in the wild a cleaner wrasse (Labroides sp.) will help them by taking parasites from their bodies, however these wrasses are extremely difficult to sustain in captivity. Alternative fish such as Neon Gobies (Gobiosoma spp.) or cleaner shrimp can help them by providing this cleaning service in the home aquarium.  As for treatment, some tangs are sensitive to copper because they have an important microfauna in their digestive system, soprolonged or continuous use of a copper treatment is not advisable.  It is also said that pellets soaked in garlic may help fend off Marine Ich.

   Providing a vitamin supplement (including vitamin C) can help provide for their nutritional needs, and vitamin C can help reduce Lateral Line Erosion (LLE) which may be caused by activated carbon. Enriching foods can be done by soaking dried pellets with liquid vitamins, adding vitamins to the food, or adding a liquid vitamin into the water. . Some hobbyists also report success with supplemental foods such as previously boiled or frozen zucchini, broccoli, spinach, and leaf lettuce.

  The best routine is a quarantine tank and a stress free environment with good quality veggie foods, places to hide and a quiet area for the aquarium.  

   For more information see Fish diseases.


The Brown Surgeonfish or Lavender Tang is seasonal.  They are not available in late summer, yet when available they are around $40.00.  (2014)


Animal-World References: Marine and Reef

Acanthurus nigrofuscus

Growth and longevity in acanthurid fishes; an analysis of otolith increments
Department of Marine Biology, James Cook University, Townsvill, Queensland 4811 Australia
By J. H. Coat and L. M. Axe

-ADW Animal Diversity Web
AcanthuridaeSurgeonfishes, tangs, unicornfishes
By: R. Jamil Jonna

-ICHTHYOLOGY at the Florida Museum of Natural History
Education Biological Profiles:  Reproduction
By Cathleen Bester


AQUARIUM FISH:  Surgeonfishes, A.K.A. the Tangs
By James W. Fatherree, M.Sc.
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