Description
This is a marine species
The Convict Tang (Acanthurus triostegus), also known as the Convict Surgeonfish, is a widely distributed herbivorous marine species found throughout the Indo-Pacific, including coral reefs, lagoons, and reef flats. Named for its bold black vertical stripes over a pale white to yellowish body, the Convict Tang is one of the most peaceful members of the tang family and is often seen schooling in large groups in the wild. Its constant grazing behaviour makes it a beneficial addition to reef aquariums, where it helps control algae naturally.
Features of the Convict Tang
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Grows up to 20–25 cm in length
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Characterised by 6 prominent vertical black bands over a pale body
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Peaceful and social, often seen schooling with conspecifics
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Requires high swimming space and well-oxygenated water
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Has a scalpel-like spine near the tail used for defence
The best aquarium size for the Convict Tang
A minimum tank size of 400 litres is recommended for a single adult Convict Tang. For groups or mixed tang setups, tanks over 600 litres with long horizontal swimming space are essential. This species is an active swimmer and becomes stressed in confined or poorly circulated environments.
Tank Mate Compatibility for the Convict Tang
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Yellow Tang (Zebrasoma flavescens)
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Green Chromis (Chromis viridis)
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Ocellaris Clownfish (Amphiprion ocellaris)
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Banggai Cardinalfish (Pterapogon kauderni)
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Cleaner Wrasse (Labroides dimidiatus)
Diet for the Convict Tang
A strict herbivore, the Convict Tang should be offered a diet rich in marine algae and plant-based material. Feed dried seaweed (nori), spirulina-based pellets, and blanched leafy greens daily. Supplement with occasional frozen herbivore blends to maintain optimal health and colouration. Constant grazing on live rock algae also supports natural feeding behaviour.
Aquarium Setup Convict Tang
Aquarium Filtration
High-capacity biological and mechanical filtration is required due to the species’ size and high activity level. A protein skimmer and strong water flow help maintain oxygen levels and water clarity.
Aquarium Plants
While marine macroalgae like Chaetomorpha or Gracilaria are not essential in the display tank, they can be grown in a refugium to supplement the tang’s herbivorous diet and help with nutrient control.
Aquarium Lighting
Moderate to high reef lighting supports algae growth for natural grazing and benefits coral if present. Maintain a consistent light schedule to support tank stability and biological rhythms.
Aquarium Heating
Keep water temperature stable between 24–27°C using a reliable heater and thermostat. Avoid fluctuations, particularly in tanks with multiple tangs.
Aquarium Substrate
A fine to medium-grade aragonite sand bed is ideal, helping to buffer pH while supporting natural reef aesthetics. The Convict Tang does not interact directly with the substrate but benefits from a clean and stable environment.
Aquarium Decorations
Live rock structures should be arranged to allow open swimming lanes and multiple grazing surfaces. Include caves and overhangs for shelter during resting periods, but preserve wide areas of unobstructed water column for free movement. Coral-safe and non-aggressive, the Convict Tang integrates well into peaceful reef systems.
