Convict Tang - Acanthurus triostegus

Convict Tang (Acanthurus triostegus)

The Convict Tang is a striking marine surgeonfish recognised for its pale silver-white body and bold black vertical bands. In the wild it is found across the Indo-Pacific on shallow reefs and nearshore habitats, often grazing in groups over algae-covered rock and coral areas. In aquaria it is an active, constantly moving herbivore that does best in a spacious, mature marine system with excellent water quality and plenty of swimming room. While generally more manageable than some tangs, it still needs proper space and stable conditions, so it is usually best suited to aquarists with at least some marine experience.

Common Name:
Convict Tang, also commonly known as the Convict Surgeonfish.

Scientific Name (Latin):
Acanthurus triostegus

Maximum Size:
Up to 20 cm in captivity.

Water Type:
Marine.

Origin / Natural Habitat:
Widespread across the Indo-Pacific, occurring on coral reefs, tidepools and other shallow nearshore marine habitats. It is especially associated with tropical reef environments and shallow grazing areas.

Water Parameters:
Temperature: 22–26°C
pH Range: 8.1–8.4
Salinity: 1.020–1.025 SG

Temperament:
Semi-aggressive. It is usually less confrontational than some other tangs, but it can still become territorial, particularly towards other tangs or similarly shaped fish if space is limited.

Diet:
Herbivorous / algivorous. It should be offered a diet rich in marine algae and seaweed, with regular grazing opportunities and supplementary prepared foods for herbivores.

Minimum Tank Size:
At least 500 litres is a sensible long-term minimum, based on trade guidance of roughly 125–130 gallons.

Behaviour & Activity:
A very active open-water grazer that spends much of the day moving through the aquarium and browsing surfaces for algae. In nature it may occur in large grazing groups, which reflects its constant, energetic behaviour in captivity.

Reef Safe:
Reef Safe
This species is widely sold as suitable for reef aquaria and is generally considered safe with corals.

Special Requirements or Care Notes:
Best kept in a mature marine aquarium with strong water movement, high oxygenation, stable water quality and plenty of room to swim. Like other tangs, it benefits from regular algae-based feeding and should be introduced thoughtfully if housed with other surgeonfish.

Suitable for:
Intermediate fishkeepers. LiveAquaria lists its care level as moderate, which fits well with its active nature and tank-size needs.

Availability:
Occasional in trade.