Acanthurus triostegus (Convict Tang)

Description:
The Acanthurus triostegus, commonly known as the Convict Tang or Barred Surgeonfish, is a distinctive species of tang that is easily recognizable due to its black and white striped body. The fish has a sleek, oval body shape typical of tangs, and the vertical black bars across its white or pale yellow body give it the "convict" name. These stripes are bold and striking, making the Convict Tang one of the most visually interesting tang species.
Native to the Indo-Pacific region, including areas around Hawaii, the Philippines, and parts of the Pacific Ocean, the Convict Tang is found in shallow reefs and lagoons, often near rocky areas or coral outcrops. The fish has a relatively small maximum size of around 6 inches (15 cm), making it one of the smaller tang species, and this makes it suitable for medium-sized aquariums.
Like other tang species, the Convict Tang has a sharp spine located on either side of its tail, which it uses as a defense mechanism.
Care:
Tank Size: Despite being one of the smaller tangs, the Convict Tang still requires a minimum tank size of 75 gallons. A larger tank, such as 100 gallons or more, is preferable for optimal health, allowing for more swimming space and grazing opportunities. These fish are active swimmers and need space to move around.
Water Conditions: The Convict Tang is fairly hardy and can adapt to a range of water conditions. However, for optimal health, the following water parameters should be maintained:
Temperature: 74-80°F (23-27°C)
Salinity: 1.023-1.025 specific gravity
pH: 8.1-8.4
Ammonia, Nitrite: 0 ppm
Nitrate: Less than 10 ppm
Regular water changes (10-20% every two weeks) and a high-quality filtration system are important to maintain excellent water quality, which is vital for the overall health of the Convict Tang.
Diet: The Convict Tang is an herbivore, and its diet should primarily consist of algae. In the wild, it feeds on a variety of marine algae. In captivity, you should provide a vegetable-based diet, including:
Algae sheets (nori, spirulina)
Marine algae (like chaetomorpha or gracilaria)
Vegetable-based pellets or flakes
Fresh vegetables such as spinach, zucchini, or broccoli
To supplement their diet, offering frozen foods like mysis shrimp or brine shrimp can help provide additional nutrients and variety.
The Convict Tang is also known for its algae-grazing habits, so allowing some natural algae growth in the tank is beneficial. You can also use a algae reactor to grow additional algae for them to graze on.
Tank Setup: Like most tang species, the Convict Tang thrives in a reef-like environment with live rock to graze on, hide, and establish territories. They also appreciate a sandy substrate for resting and hiding. Since these fish are active swimmers, having open swimming space is crucial.
It’s also beneficial to have some natural algae growth in the tank, as this will provide them with a food source. Moderate to strong water flow should be maintained, which will replicate the ocean current they would experience in the wild.
Social Behavior: The Convict Tang is generally a peaceful fish, though it can be a bit territorial toward other tangs or similarly shaped fish. This is less of an issue in a larger tank where there is plenty of space. It is usually best kept as a single specimen or in a school of 2-3 individuals in a very large tank to minimize territorial disputes.
They do well with other peaceful species, such as:
Clownfish
Wrasses
Gobies
Blennies
Anthias
Other reef-safe fish
However, it’s recommended to avoid keeping them with other tang species in a small tank, as tangs can sometimes be aggressive toward one another, especially if their territories overlap.
Companions: The Convict Tang is compatible with a wide variety of peaceful reef fish, including:
Clownfish
Wrasses
Gobies
Blennies
Anthias
Other peaceful reef fish
Avoid keeping them with overly aggressive fish or other tangs unless the tank is large enough to allow each fish to establish its own territory.
Maintenance: Regular maintenance is important to keep the Convict Tang healthy. This includes:
Routine water changes (10-20% every two weeks)
Using a protein skimmer to remove excess organic waste
Maintaining efficient filtration to keep water quality high
Regular algae management in the tank to ensure the Convict Tang has sufficient grazing material
Regularly monitor water quality and make sure the algae supply is well-maintained to keep the fish active and healthy.
Additional Considerations:
Health Concerns: Like other tangs, the Convict Tang is susceptible to marine ich (Cryptocaryon irritans) and other parasitic diseases, particularly when stressed or when water quality is poor. Regularly checking water quality, quarantining new fish, and monitoring for signs of disease will help prevent most health issues.
Size and Space: Though the Convict Tang is smaller than many other tangs, it is still an active swimmer that requires enough space to move around. Overcrowding in a small tank can lead to stress and potential health issues.
Temperament: The Convict Tang is generally peaceful, but as a surgeonfish, it can become more territorial in smaller tanks. Ensuring that the tank is large enough and well-planted with hiding spots can help minimize aggression. They are best kept in a peaceful community tank with other non-aggressive species.