Blue-eyed Tang

Blue-eyed Tang

The Blue-eyed Tang (Ctenochaetus binotatus), or twospot bristletooth, is a hard-working member of the surgeonfish family. Warm brown with fine blue spotting and lines and a pair of dark spots at the base of the dorsal and anal fins, it is more understated than the showy sailfin tangs — but its real value lies in its mouth. As a bristletooth, it has comb-like teeth adapted to scoop up the film of detritus and microalgae that coats reef surfaces, making it one of the best natural clean-up grazers in a reef tank.

Peaceful by tang standards and genuinely useful, it is a popular working fish for established reef aquariums.

Natural Habitat & Origin

Ctenochaetus binotatus is widespread across the Indo-Pacific, from East Africa to the Tuamotu Islands and from southern Japan to New South Wales. It inhabits deep lagoons and seaward reefs in areas of coral and rubble, down to around 60 metres (200 feet), where it grazes constantly over rock and sand surfaces.

In the aquarium it wants abundant live rock with grazing surfaces and open swimming space, in a mature system that produces the film algae and detritus it feeds on.

Care Requirements

Maintain stable marine conditions: salinity around 1.024–1.026, pH 8.1–8.4, and a temperature of about 24–26°C (75–79°F), with good flow. Reaching about 22 cm (8.7 inches), it needs a roomy tank of around 340 litres (about 90 US gallons) or more for swimming and grazing. It is hardy and adaptable, settling well into a mature reef.

Diet & Feeding

The Blue-eyed Tang grazes on the film of detritus and microalgae (including diatoms and similar) rather than long filamentous algae, using its bristle-like teeth to scoop it from surfaces. Support this with a plant-based diet: dried marine algae (nori) on a clip, herbivore and spirulina preparations, and algae-based frozen foods. A mature tank with plenty of grazing surface is ideal, and its grazing helps keep nuisance film algae and detritus in check.

Behavior & Temperament

This is a relatively peaceful surgeonfish, though like all tangs it can be territorial toward others of its kind, especially other bristletooths. It is best kept as the only Ctenochaetus in most tanks. Toward unrelated species it is generally well behaved, spending its day methodically grazing. Its caudal spine is a defensive weapon, so handle with care.

Tank Mates

House it with a wide range of peaceful to semi-aggressive reef fish — other (dissimilar) tangs given space, wrasses, angelfish, anthias, clownfish and similar. Avoid pairing it with another bristletooth in a small system. It is reef-safe, grazing surfaces rather than corals or invertebrates, making it an excellent clean-up addition to a reef.

Breeding

Ctenochaetus binotatus is a pelagic spawner with planktonic larvae and is not bred in the home aquarium. Trade specimens are wild-collected.

Common Health Issues

Like other surgeonfish, the Blue-eyed Tang is susceptible to marine ich (Cryptocaryon irritans) and marine velvet (Amyloodinium ocellatum), especially when stressed. Quarantine new arrivals, keep water quality stable, and provide good flow and grazing surfaces. Given a mature reef and a varied algae-based diet, it is a hardy, peaceful and genuinely useful tang for an intermediate keeper.