Convict Tang
Convict Tang
Goes well with:
FAQs Answers to the most common questions.
How do I tell a Convict Tang apart from other Acanthurus tangs, and what size should I expect it to reach?
A Convict Tang is usually identified by its bold vertical black-and-white striping as a juvenile, which changes somewhat as it matures but stays distinctly “barred” compared with most tangs. It is a stout, laterally compressed Acanthurus tang from the Indo-Pacific. In captivity, expect roughly 8 to 10 inches as an adult, with some individuals getting a bit larger in very spacious systems. The species is often confused with juvenile surgeonfishes that have stripes, so the key is the overall body shape, the surgeon’s scalpel near the tail, and the pattern consistency across the flanks.
What tank size and aquascape does a Convict Tang really need to thrive long-term?
This is not a small-tank tang. A single Convict Tang should be kept in a large, mature system, ideally 180 gallons or more, with a long swim path and strong circulation. They are active grazers and constant cruisers, so footprint matters more than just total water volume. The aquascape should leave open swimming lanes while still providing plenty of rockwork for grazing and shelter. They do best in an established reef-style system with stable parameters and lots of natural algae growth or frequent algae-based feeding.
Are Convict Tangs reef safe, and will they damage corals or other invertebrates?
Yes, they are generally considered reef safe with corals and most invertebrates. They do not typically nip coral polyps or consume sessile invertebrates. The main “reef issue” is not coral damage but their grazing behavior and temperament: they may pick at nuisance algae, film algae, and sometimes very fine macroalgae, and they can become territorial toward other tangs or similarly shaped fish. In a reef aquarium, they are usually a good fit as long as you manage aggression and give them enough space.
What should I feed a Convict Tang to keep its color, digestion, and immune system in good shape?
A Convict Tang should get a mostly herbivorous diet with frequent feedings. Base foods should include marine algae sheets (especially nori), spirulina-based foods, algae pellets, and herbivore frozen foods. Supplement with small amounts of mysis, brine shrimp, and other meaty foods, but don’t make those the staple. Because tangs have long digestive tracts built for constant grazing, they do best with multiple small feedings per day rather than one large meal. Strong coloration and good body condition usually come from consistent algae intake plus very clean water and low stress.
Is a Convict Tang aggressive, and can I keep it with other tangs or surgeonfish?
Convict Tangs can be quite assertive, especially as they mature. They are often less famously aggressive than some other Acanthurus species, but they still need careful planning if you want multiple tangs in one aquarium. They are best added early or introduced in a carefully structured stocking plan. Avoid keeping them with similarly shaped or similarly colored surgeonfish in cramped tanks, because body shape competition can trigger chasing and stress. In larger systems, they can coexist with other tangs if the tank is spacious, has multiple feeding stations, and territories are broken up with rockwork.
All listed sizes are approximate, not guaranteed, and may vary slightly.
The Convict Tang, Acanthurus triostegus, is a distinctive saltwater fish recognized for its pale silver-white to gray body crossed by bold black vertical bars. Its clean, high-contrast pattern gives it an unmistakable appearance, while its streamlined shape and constant grazing activity add movement to both reef aquariums and fish-only marine displays.
This species has an exceptionally broad natural distribution across much of the Indo-Pacific and into the eastern Pacific. Convict Tangs inhabit lagoons, shallow reefs, and seaward reef habitats with hard substrates, where they frequently graze filamentous algae from rock surfaces. They are often encountered feeding in groups in the wild. Their active grazing behavior, manageable adult size compared with many larger surgeonfish, and generally moderate temperament make them an appealing choice for established saltwater aquariums with adequate swimming space.
Quick Care Guide
Care Level: Moderate
Minimum Tank Size: 130 gallons
Temperament: Semi-aggressive
Diet: Herbivore
Reef Safe: Yes
Region: Indo-Pacific and Eastern Pacific
Scientific Name: Acanthurus triostegus
Tank Requirements
The Convict Tang requires a spacious, established marine aquarium with substantial open swimming room and mature rockwork for grazing. A 130-gallon or larger aquarium is recommended for long-term housing.
Arrange live rock to create caves and sheltered resting areas while maintaining long, unobstructed swimming lanes. Mature rock surfaces are particularly beneficial because this species naturally spends much of the day grazing algae and other plant material from hard substrates.
Moderate to strong water movement, excellent oxygenation, and efficient biological filtration are recommended. Like other active surgeonfish, the Convict Tang performs best in stable, well-maintained systems with consistent water quality. A secure aquarium cover is also advisable, particularly during introduction and acclimation.
Diet and Feeding
The Convict Tang is primarily herbivorous and naturally feeds heavily on filamentous algae. Its captive diet should therefore emphasize marine algae and high-quality vegetable-based foods.
Offer dried marine algae or nori daily, along with spirulina-based flakes or pellets, quality herbivore pellets, and frozen preparations formulated for marine grazers. Established live rock provides additional opportunities for natural grazing throughout the day.
Mysis shrimp, enriched brine shrimp, and other meaty foods may be consumed when offered to tankmates, but these should supplement rather than replace an algae-rich diet. Several smaller feeding opportunities throughout the day are ideal for supporting its natural grazing behavior and maintaining good body condition.
Temperament and Tankmates
The Convict Tang is generally less aggressively territorial than many surgeonfish, but it should still be considered semi-aggressive, particularly around other tangs competing for grazing territory.
Suitable tankmates include clownfish, anthias, wrasses, gobies, blennies, rabbitfish, angelfish, and many other appropriately sized marine community fish. Greater care should be taken when combining it with other surgeonfish, especially similarly shaped species.
Convict Tangs naturally form feeding groups, but this behavior does not mean a group is appropriate for an average home aquarium. Keeping multiple specimens requires substantially more space, abundant food, and careful introduction to reduce territorial disputes.
Reef Compatibility
The Convict Tang is considered reef safe and is well suited to appropriately sized reef aquariums. Its feeding behavior is focused primarily on algae growing across rockwork and other hard surfaces rather than healthy coral tissue.
It does not normally prey on ornamental shrimp, crabs, snails, clams, or other common reef invertebrates. Its persistent grazing can also make it a useful addition to established reef systems where natural algae growth is available.
Supplemental feeding remains essential even in aquariums with visible algae, as natural growth alone may not provide sufficient nutrition.
Water Parameters
Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH
Stable conditions are more important than repeatedly adjusting the aquarium to achieve an exact value. Maintain consistent salinity and temperature along with strong oxygenation, reliable filtration, and regular aquarium maintenance.
Common Considerations
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Active swimmer: Provide generous open swimming space in addition to mature rockwork and grazing surfaces.
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Frequent grazer: Marine algae should be offered regularly to support its herbivorous diet and natural feeding behavior.
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Tang compatibility: Although often less confrontational than many surgeonfish, territorial aggression can occur toward other tangs and similarly shaped competitors.
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Group housing requires space: Wild schooling behavior should not be interpreted as suitability for keeping several specimens in a typical aquarium.
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Caudal spine: Like other surgeonfish, it possesses a sharp defensive spine near the base of the tail and should be handled carefully during capture or transfer.
