The Achilles Tang is appropriately named, bringing to mind the Greek hero, Achilles, who had a flaw of vulnerability that proved fatal, thus the term “Achilles Heel.”

The Achilles Tang is a deep-bodied, flat, oval-shaped fish with seriously quick swimming abilities.  They are dark brownish black with electric blue pin striping around their eyes, mouth area, at the outer edges of the continuous dorsal fin and the anal fin and some blue around the chin area.  Most have orange accenting, however, a few have red accents, which is why some common names are Redspot or Redtail Surgeonfish.  Near the tail fin is an orange or red teardrop shape, pointing towards the tail fin, and within that orange or red or red area is the very sharp scalpel or spine used to defend themselves.  Juveniles lack this orange or red spot and have a line in that area instead.  The actual tail fin is dark at the base, followed by a wide orange or red vertical tail shaped band, then trimmed in black and followed by a white outer edge.  The other areas that are accented in white are a small area on the edge of the gills, and a ring around the mouth, and a thin white line on the outer edge of the body, just under the dorsal and anal fins.  There is also an orange or red line right above this white line on the body.  The Achilles Tang grows to 9.4”(24 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).  This fish is best kept by advanced aquarists.  

So what do we call them?  Are they “tangs,” “surgeonfish” or “doctorfish?”  While all 3 are correct, however only two of those words (doctor and surgeon), are easy to figure out, referring to the very sharp scalpel-like spine located on the caudal peduncle.  Are you still wondering about the term, “tang?”  Yeah, I was too, since it is not a term we commonly find in our vernacular these days, yet it is a fairly simple word that most of us prefer to use.  Tang is defined as:  “a projecting shank, prong, fang, as on a knife, file or sword, connected with a handle.”  And you thought it had to do with that tangy orange or red drink!  To go along with this definition, the Achilles Tang has a deep groove on each side of the caudal peduncle, which is the fleshy area right before the tail fin.  Within each groove is a very sharp, scalpel-like, retractile spine or “tang,” which can be flipped out into an erect weapon when the tail fin is swiped sideways toward what is threatening the fish.  This weapon is highlighted in orange or red, which serves as a warning to other fish!  That sharp weapon definitely carries the definition of a “tang!”  The Achilles will also lighten their bodies to make pieces of flesh or parasites more visible for the cleaner fish or shrimp to remove.  

The Achilles Tang is best left to advanced aquarists due to their very specific needs, tank size, tank age, location, propensity to be ill, and tank mates.  They are best kept as the only tang in the tank and the tank should be located in a calm part of the house/apartment/condo/etc., to help keep stress levels low.  This fact is backed by many aquarist who have had success with this fish. They need to be well fed, at least 3 times a day, with a variety of veggie foods and some meat, although a piece of Nori or other seaweed sheets affixed to a rock with a rubber band, in-between meals is essential.  Some may adapt to the veggie clip over time, but many will not. They are best kept in a reef like setting, not a fish only community, as some successful aquarist have noted.

Unless your tank is 10 feet long and divided by rock to establish boundaries, do not house the Achilles Tang with other tangs.  In this instance, the Achilles should be not only the largest tang, but should be added last due to their aggressive nature.  One aquarist added an Achilles tang that was twice the size of a resident powder blue in his 10 foot tank, and had success, however few aquarist have tanks this size!  Even in a huge tank, do not house with Sohal Tangs or other similarly angry tangs. Do not house with any aggressive fish such as triggerfish.  So just say, “NO!” to other tangs if you want some measure of success with the Achilles Tang.  The first step is acquiring a healthy, fat, eating specimen with no injuries and is at least 5” long.  Tank should be mature, with good lighting to grow algae and at least 6 feet long.  The Achilles Tang will not bother any peaceful fish or small semi-aggressive fish, which are the best tank mates.  They MUST be the dominant fish to reduce stress which leads to illnesses.

House your beautiful Achilles Tang in a 150 to 180 gallon tank that is at least 6 feet long.  There are various tank configurations, however longer is better than taller with these fish.  Provide places for them to hide within the rock work when frightened and swift water movement in at least in one area of the tank.  For me it was the back of the tank, accessible to the tang, but absent of corals and he loved his “water treadmill!”  Good oxygenation with lower water temperatures, a good skimmer and a sandy substate to allow them to “blow” the sand with their mouth, searching for foods.  Feed them several times a day with foods that have marine algae and Spirulina and sushi nori.  Mine enjoyed bananas, pineapple and mango as a treat!  The more varied the diet the better, and you may feed blanched broccoli, zucchini, leaf lettuce and other veggies as a treat but stick to marine greens as the staple of their diet since there is more calories and nutrition.  Also feed pellets with high protein and garlic to supplement their veggie diet can be given.  Live mysis gut loaded with spirulina flake can encourage them to start feeding, however this is a poor nutritionally based food for them.  They do best in a reef that has ocean salinity, naturally growing algae due to more intense lighting and other natural foods not found in fish only tanks.  

Scientific Classification

Species: achilles

Achilles Tang – Quick Aquarium Care

Aquarist Experience Level:Advanced
Aquarium Hardiness:Difficult
Minimum Tank Size:180 gal (681 L)
Size of fish – inches:9.4 inches (23.88 cm)
Temperature:72.0 to 78.0° F (22.2 to 25.6&deg C)
Range ph:8.1-8.4
Diet Type: Herbivore
Achilles Tang
Image Credit: Vojce, Shutterstock

Habitat: Distribution / Background

The Achilles Tang, Acanthurus achilles, was first described by Shaw, in 1803.  The name Acanthurus is greek for “thorn tail.”  Some of the common names are Achilles Tang, Redspot Surgeonfish, Redtail Surgeonfish, Orangespot Surgeonfish, and Achilles Surgeonfish. The name Achilles comes from the mythical story of the 1/2 human son of the sea-nymph, Thetis.  Achilles the Myrmidon’s mother, Thetis, dipped him as a baby, into the river Styx to make him invincible.  Her mistake, was that she held him by his ankles, preventing the water from contacting his skin near the ankles and heels.  This created a fatal flaw for Achilles!  He was killed by a single poison arrow that was shot into his heel.  The term “Achilles tendon” or Achilles heel” became a common term used to describe a fatal mistake or flaw in someone or something.  George Shaw, who recorded the species in 1803, likened the blood-red (or orange or red) spot on the Achilles Tang’s tail to that mythical bleeding heel of Achilles.  The irony is the name Achilles Tang also describes how easy this fish can be killed in captivity while seemingly hearty in the ocean!

The Achilles Tang is found in the Western Pacific Ocean from the Oceanic Islands to the Hawaiian, Pitcairn, Wake, Marcus, and Marianna Islands.  In the Eastern Central Pacific Ocean, they are found at the southern tip of Baja California, Mexico and offshore Islands.  They are found in groups in clear seaward reefs, feeding on filamentous algae and macro algae, along with any meaty organism dwelling within these foods.  The depths they are found in are only up to 13 feet (0 to 4m), so their environment includes high oxygen levels and very strong water movement.  They have been known to hybridize with the White Cheek Tang (Acanthurus nigricans) in the wild.   

  • Scientific Name: Acanthurus achilles
  • Social Grouping: Groups – Although they are found in groups in the open ocean, they should be housed singly in captivity.
  • IUCN Red List: LC – Least Concern – The Achilles Tang is on the IUCN Red List of Threatened Species under “least concern.”


The Achilles Tang is a deep bodied, laterally compressed, oval shaped fish with seriously quick swimming abilities.  They are dark brownish black with electric blue pin striping around their eyes, mouth area and at the outer edges of the continuous dorsal fin and the anal fin.  Their mouth protrudes slightly, used for grazing on algae in hard to reach areas.  The caudal peduncle has an orange or red teardrop shape, pointing towards the tail fin, and within that orange or red area is the very sharp scalpel or spine that faces forward, used to defend themselves.  The actual tail fin is dark at the base, progressing to a wide vertical lyre shape orange or red portion that is followed in a black pin striped and followed by a white outer edge.  The other areas that are accented in white are a small area on the edge of the gill plate, around the mouth, and on the outer edge of the body just under the dorsal and anal fins.  The orange or red is also found as a thin line above this white pin striping.  The pelvic fins also have one spine and the anal fin has 3 spines.   Juveniles lack the orange or red teardrop spot on the area near the tail fin, however they have an orange to red line that grows with age.  The Achilles Tang female is larger and grows to 9.4” (24 cm), and most tangs live 30 to 45 years (Choat, Axe 1996), however in captivity it can be drastically reduced.

  • Size of fish – inches: 9.4 inches (23.88 cm)
  • Lifespan: 30 years – 30 to 45 years (Choat and Axe 1996), possibly less in captivity.

Fish Keeping Difficulty

The Achilles Tang is a difficult tang to keep in captivity.  First and foremost, do not use activated carbon, since it has been scientifically linked to Lateral Line Disease.  When capturing your tang, use a container, not a net, due to the various spines they have on their tail, anal and pelvic fins.  This fish is a very active swimmer and needs to be in a tank that is at least 6 feet long, preferably a minimum tank size of 180 gallons.  Ideally, they should be the only tang in this minimum tank size due to the mass amounts of algae they consume and aggressive nature. The aquarium should be mature enough to produce plenty of algae to feed on, before adding your Achilles Tang.  Being HUGE eaters due to their high energy output, in between feedings, provide a Nori or other preferred algae sheets and rubber band it to a rock.  Feed them 3 times a day with combination of high quality Spirulina flake or pellet, broccoli and other veggies, which will help them get the calories they need.  Keep the oxygen levels up with a good skimmer, lower temperatures, and have a linear power head blowing across an open area in the back of the tank.  The reason for this is that corals and most fish will not enjoy this fast movement, so they can occupy the front area of the tank.  The Achilles Tang will use this frequently to swim against, to satisfy their need to “exercise” in this sort of “underwater treadmill.”  My tang would regularly hop to the back of the tank and swim against a strong linear power head then come back to the front and calmly pick at algae!  It was kind of funny to watch!  The other fish avoided the back of the tank like the plague!  This emphasizes the reason for tank size.  Having a 6 foot tank that is at least 18 to 24” from the front to the back wall provides this little exercise area which I personally feel all tangs appreciate!  Clean water is essential in keeping these tangs, which is another reason why larger tanks are suggested.  “Dilution is the solution,” as they say!  

  • Aquarium Hardiness: Difficult
  • Aquarist Experience Level: Advanced

Foods and Feeding

The Achilles Tang is an herbivore.  Of all the genus of tangs, the Acanthurus are the largest algae/veggie eaters in the family.  Although they will benefit from some meaty foods like mysis shrimp that may be given to initiate a feeding response, the bulk of their foods come from veggie sources.  Feed them a good spirulina based flake or pellet, blanched broccoli, leaf lettuce, zucchini and other veggies.  Each tang will have their own favorites and they do enjoy certain fruits, so experiment but make sure the fruits are more of a treat than a main staple.  Feed them 3 times a day and keep a Nori or other algae sheet rubber banded to a rock in-between feeding.  It is helpful to add Selcon or vitamins specifically for marine fish to some of the food (follow directions on the product)

  • Diet Type: Herbivore
  • Flake Food: Yes – The food should have Spirulina in it.
  • Tablet / Pellet: Yes – The food should have Spirulina in it.
  • Live foods (fishes, shrimps, worms): Some of Diet – If fish is not eating, gut filling live mysis or brine shrimp with spirulina flake may initiate a feeding response.
  • Vegetable Food: Most of Diet – Probably about 90% of the diet.
  • Meaty Food: Some of Diet – Only 10%, however in a reef tank, copepods will be ingested with naturally growing algae and supplementing will not be necessary.
  • Feeding Frequency: Daily – 3 times a day with algae sheets affixed to rocks in between feedings.
Achilles Tang in Aquarium
Image Credit: iliuta goean, Shutterstock

Aquarium Care

These fish are quick and agile swimmers, spending a good deal of its time in the open water and moving in and out of crevices. 

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

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. 

  • Water Changes: Bi-weekly

Aquarium Setup

Minimum tank size is 180 gallons to provide the length and depth and surface space for algae to grow on live rock and provide plenty of swimming space for this mover and shaker!   Do not house in a nano tank, as they will outgrow it too fast and it will cause aggression.  Provide live rock with plenty of places for them to hide and sleep in.  Any substrate is acceptable; however, they do enjoy blowing sand around as they look for food.  Light should be high enough to provide algae growth for your massive veggie eater and the tank should be mature enough to have stable water and plenty of natural algae growth before adding your Achilles Tang.  The shallow waters they are found in are typically around 78 to 83˚F (26 to 28˚C) in the summer.  This would mean those temperatures are temporary and they do better in lower temperatures from 72 to 78˚F (23 to 26˚F).  Long-term exposure to 79 to 83˚F, according to some experts, may prove detrimental over 4 or 5 months.  Also, lower temperatures in water provide higher oxygen saturation, which is what these very active swimmers need.  They do well at the normal ocean salinity of 1.023 and pH between 8.1 and 8.4, however, both of these qualities, especially the pH should be stable.  They swim very fast and appreciate at least one area of the tank (preferably the back of the tank where corals are not located) to have a strong powerhead blowing a linear flow across the back to swim against.  They swim at all levels of the tank and should be the only Acanthurus in the tank unless it is 400 to 500 gallons and 10 feet long to establish territory. 

  • Minimum Tank Size: 180 gal (681 L) – Tank configuration should be at least 6 feet long.
  • Suitable for Nano Tank: No
  • Live Rock Requirement: Typical Plus Hiding Places
  • Lighting Needs: Moderate – normal lighting – High enough to produce algae growth.
  • Temperature: 72.0 to 78.0° F (22.2 to 25.6&deg C) – Lower temperatures provide the much needed higher oxygen levels. They can tolerate up to 83˚F for 3 or 4 months, which is typical for the summers in the oceans they live in, however this should not be done long term.

  • Breeding Temperature: – Unknown
  • Specific gravity: 1.023-1.025 SG
  • Range ph: 8.1-8.4
  • Brackish: No
  • Water Movement: Strong – Provide one area of the tank with a strong linear water flow, preferably the back wall away from corals.
  • Water Region: All

Social Behaviors

The Achilles Tang are the most aggressive of the Acanthurus and should be the only Acanthurus in the tank.  There should also only be one Achilles Tang in the tank.  They do not do well in groups, even if the tank is hundreds of gallons.  The only exception to adding another Acanthurus is if the tank is say, 10 feet long and they are twice as big as the other Acanthurus as the time of adding them to the tank, as was experienced by one aquarist.  This may even be the exception to the rule, since there is no way of knowing gender, and in that case of the 10 foot tank, both may have been females.

The Achilles Tang will get along with tangs from other genus that are not aggressive, but only in a tank that is hundreds of gallons.  They will stress out in the presence of other tangs and are quite aggressive towards them, causing yet a second stress that can make them sick.  The great thing about Achilles Tangs is they will not bother even the smallest, most peaceful goby, blenny or other peaceful fish.  They ignore anthias, fairy and flasher wrasses and even large peaceful fish.  Aggressive tangs like the Sohal Tang, Triggers, Puffers and other larger and more aggressive fish should be left out of the equation when putting tank mates together.  Essentially, the Achilles Tang should be the only tang and the largest fish in the tank, which will be void of any aggressive fish including dottybacks and aggressive clowns like Maroon Clownfish, unless the tank is hundreds of gallons.  The key is a stress free, reef environment with no competition for foods from other herbivores.  Small dwarf angelfish that are more chill, like the Coral Beauty should be fine.  Large angelfish should not be housed with your Achilles Tang unless they are planktivores, who will not complete for veggie foods.

Although literature states that the Achilles Tang will nip at large-polyp stony corals, most aquarists to feed their tang properly will not run into this problem.  Personally, my Achilles never bothered any of my LPS, however it would pick at any algae at the base of the coral, which was a great service to the coral!

Inverts are not at risk, however a copepod or amphipod may be eaten here or there while the tang grazes on the algae in which they live.  On a rare occasion, an occasional tang will find the slime that clams produce quite tasty.  While the tang is not biting the clam, the action causes the clam to close often, stressing the clam and eventually this stress will kill the clam.  This shouldn’t be a problem with a well fed tang.

  • Venomous: No
  • Temperament: Aggressive – Although tangs are considered semi-aggressive, the Achilles Tang is one of the most aggressive tang, however they are peaceful toward all other non-tang fish.
  • Compatible with:
    • Same species – conspecifics: No
    • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Safe
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Safe
    • Monitor – Certain aggressive dottyback and damselfish will pick on a young Achilles Tang and stress them out unless tank is hundreds of gallons. Best to pass on this group.
    • Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor – In minimum tank size, the Achilles Tang should be the only tang. Only tangs from other genus in hundreds of gallons. Only large angelfish that are planktivores. Large wrasses will not bother your Achilles Tang, however the constant swimming may stress your tang out.
    • Monitor – Seahorses and most pipefish need their own tank. Mandarins will not be bothered.
    • Anemones: Safe
    • Mushroom Anemones – Corallimorphs: Safe
    • LPS corals: Monitor – Should not bother LPS if well fed.
    • 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: Monitor – A very RARE tang will find the slime clams produce yummy, causing the clam to close and stress.
    • Copepods, Amphipods, Mini Brittle Stars: Safe

Sexual differences

Unlike other genus of tangs, the Acanthurus female is larger than the male. 

Breeding / Reproduction

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. 

These fish have spawned in captivity in public aquariums (or very very large tanks), however, there hasn’t been success raising the larvae into viable fish.

Probably will not be accomplished in captivity. See the description in the Breeding Marine Fish page.

  • Ease of Breeding: Unknown – Not possible at this time.

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.  


These fish are seasonal, typically available late summer to early fall.  They range from $200.00 for a juvenile and $380.00 for an adult. (2014)  

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 Achilles Tang (Image Credit: Ltshears, Wikimedia Commons CC BY-SA 3.0 Unported)