Acanthurus Triostegus (Convict Tang)

Acanthurus Triostegus

Last updated on September 5th, 2022 at 02:24 pm

The term convict tang refers to the species Acanthurus triostegus, which is a member of the surgeonfish family (Acanthuridae). They are also commonly referred to as convict surgeonfish or convict tangs, though technically the last name should be used only when referring to members of the genus Acanthurus (to prevent confusion with other species in the family).

Acanthurus triostegus, also known as the convict tang, does not belong to any particular genus in the family Acanthuridae, but rather to the subfamily Acanthurinae which includes all acanthurids that are not damsels or angelfishes (Family Pomacentridae). Members of the subfamily are differentiated from other acanthurids by their lack of caudal fin spines and their possession of one dorsal and two anal fin spines.

Origin and descriptions

Acanthurus Triostegus

Acanthurus triostegus, commonly known as convict tang or convict surgeonfish, is a marine fish native to Indo-Pacific waters. It is also one of more than 800 species in genus Acanthurus. Acanthurus is from Ancient Greek meaning spine tail; triostegus refers to its black stripes.

The distinctive black-and-white striped body pattern of convict tang has inspired numerous myths and folklore throughout history including how they earned their name. In an early 1840s expedition, French zoologist Jean René Constant Quoy and naturalist Joseph Paul Gaimard observed these fishes near New Caledonia.

Species profile

Acanthurus Triostegus

As its name suggests, Acanthurus triostegus is a tang. Its scientific name, Acanthurus triostegus, is derived from Greek: acanthus refers to a plant that may be used for wreaths, while tri means three and stigma refers to markings or spots. Some researchers believe that convict tangs acquire their common name because they are most easily spotted when they group together at night.

The convict can also refer to behavior. In many species of fish, including Acanthurus triostegus, males cooperate in raising young communally; however, these fathers play no role in rearing their offspring after birth. The community system enables males of many fishes species to reproduce quickly and greatly increases reproductive success.

13 Popular Marine Angelfish Species (Saltwater Angelfish)


Acanthurus triostegus are found primarily in saltwater, tropical regions of Indo-Pacific oceans at depths of 5 to 110 meters. This species prefers waters with a temperature range between 72 and 78 degrees Fahrenheit and a pH level between 8.1 and 8.4.

The biggest threat to Acanthurus triostegus is overfishing, which can greatly reduce their population size. In some areas, they are so threatened that laws have been passed that prohibit harvesting them altogether.

Acanthurus triostegus size

They usually range between 3.5 and 5 inches (9.0 – 13 cm), but they have been known to reach a maximum length of 8.0 inches (20 cm) in captivity.

Acanthurus triostegus tank size

The minimum recommended tank size is 120 gallon or larger. The Acanthurus triostegus is a moderately sized fish and is best kept in a species-only aquarium as it can be aggressive toward other tangs, including its own kind.

Tank set up

While there are many ways to set up a tank for these beautiful fish, it is important to remember that they have special needs.

Because these fish come from coral reefs in saltwater environments, it is a good idea to simulate their natural environment as closely as possible by keeping them in a brackish aquarium with an appropriate amount of space and providing plenty of hiding spots such as rocks or live plants. The use of specific salts will help maintain a slightly salty pH level, which makes the water even more similar to their natural habitat. They should be kept in water between 1.005-1.010 on average and only fed food designed for brackish conditions.

Be sure to keep any marine species away from other saltwater animals due to incompatibility issues; it may be best to house your convict tangs separately from other types of tropical fish if you plan on mixing species in one tank at all.

Acanthurus triostegus tank mates

The convict tang is not a suitable species for reef aquariums but may be housed with peaceful fish such as certain damselfish.  They tend to ignore their tank mates unless threatened. They can also be combined in an aquarium if they are introduced at an early age and raised together.

What Is A Devil Fish (Mobula Mobular)?

Some other good tank mates are surgeonfish, filefish, pupfish, lionfish, and butterflyfish.

They will only get along with peaceful, non-aggressive, and reef-safe species. They do not cohabitate well with other tangs. Many people have had problems keeping them with Naso tangs, Hippo tangs, and Zebrasoma species which are also known as Zebra or Coleoid tangs.


Acanthurus Triostegus

There are many different tang species available to aquarists. However, few other than acanthurus triostegus and three other convict tangs (Paracanthurus hepatus, Zebrasoma flavescens, and Zebrasoma desjardinii), have proven themselves so readily capable of breeding in home aquariums as acanthurus triostegus.

The Convict tang is a fairly easy fish to breed. Although wild-caught specimens are often hard to convince to spawn in captivity, it can be done with relative ease if they’re captured while they’re young. They have been bred by hobbyists using both natural and artificial means.

Courtship behavior involves pairs swimming close together and touching each other with their fins. If a female becomes receptive (actively swimming towards males), spawning follows after several days of courtship behavior.

After mating, the eggs will become attached to various structures near the water surface where they will stay until hatching after about 3 – 4 days depending on temperature conditions during incubation time.

Larvae are planktonic and spend several days floating in a cloud of micro-organisms known as marine snow until their yolk sac is fully absorbed and they are able to swim independently. At that point, they settle onto a suitable substrate and begin an independent life cycle of eating and growing until maturity is reached around 2 years old or so.

Are Acanthurus triostegus aggressive or peaceful?

Acanthurus triostegus or convict tang is a moderately aggressive saltwater fish.

They are wonderful fish for any reef tank and can coexist in an aquarium with smaller fish, however, they are not to be trusted, they are likely to pick on them if not enough space is available.

Pygmy Angelfish Care (Cherubfish)

In a very large tank, it can be kept together with other Acanthuruses, yellow tangs, and blue tangs. When in doubt it’s always safer to keep several tangs in one tank, so you can have some backup and prevent overpopulation.

Acanthurus triostegus care

Acanthurus Triostegus

The convict tang is a brackish water fish and needs to be kept in a tank that has saltwater. Because of their aggressive nature, they are best kept with other tangs or a tank with numerous other fish. The water temperature should be between 72 – 78 degrees Fahrenheit and salinity between 1.020 – 1.025.

This species is reef safe and will help control green algae growth on your live rock if there is adequate space to hide within it’s rocky crevices and caves. It requires at least 30 gallons per individual and more is better when keeping multiple specimens. Add plenty of hiding places among rocks so they do not feel threatened by larger fish swimming over them. Feeding them 2 to 3 times a day will keep them healthy and thriving in your tank.

What do Acanthurus triostegus eat?

Tangs are generally a herbivore, eating marine algae and seaweed-based foods (frozen, flakes, or pellets), they can also be carnivorous in captivity, especially if a substantial amount of vegetable matter is not available for them to eat. They tend to feed on zooplankton and small crustaceans like amphipods, copepods, and euphausiids. For larger prey, they hunt down spiny lobsters, shrimp, crabs, krill, and even sea urchins.

Water parameters

Acanthurus Triostegus

Water quality is of utmost importance in setting up a successful aquarium, but it is also important to bear in mind that fish are more sensitive to certain parameters than others. For example, in an Acanthurus triostegus tank with a pH of 8.3 and 1.022 salinity, a hardness 10 dGH or more, and an increase in temperature from 28 ̊C to 29 ̊C will cause twice as much stress as an equivalent decrease from 28 ̊C to 27 ̊C.

Consequently, water changes may need to be adjusted accordingly. These guidelines assume that all other parameters remain constant for a given species; pH, carbonate hardness and any nutrient limitation or excesses should be maintained at appropriate levels for your chosen species. In some instances, where these other factors have been deemed critical, we have supplied specific notes on suitable ranges within each profile.

Clownfish Ocellaris - Description And 5 Amazing Breeding Steps

It is always advisable to speak with your local aquatic retailer regarding water parameters specific to your geographical location if you have any doubts or concerns over water quality issues prior to your purchase.

Acanthurus triostegus lifespan

They can live for 10 years or more if cared for properly.

Parasites and diseases

Because it comes from coastal regions in its native range, a quarantine period is suggested when introducing convict tangs to marine aquariums. The species is also susceptible to parasites and diseases that can easily be treated with medication. Some of its parasites and diseases are Cirrhitichthys vaigiensis, mouth fungus; Cryptocaryon irritans, Ich; Oodinium sp., skin flukes (external parasites); Uronema marinum, and velvet disease.


Juvenile Acanthurus triostegus are susceptible to predation by fish. Juveniles can also be preyed upon by predatory starfish such as Linckia laevigata. Adults can be consumed by large moray eels, giant sea bass, and sharks.

Do Acanthurus triostegus make good pets?

Yes. The good news is that it’s possible to keep a convict tang as a pet. It’s not necessarily easy, but you can do it if you commit yourself to do your research and getting set up properly before adding one of these fish to your home aquarium.

The bad news is that there are certain things about convict tang care that will be much more challenging than taking care of many other tropical fish species.