Blue Eye Tang (Ctenochaetus binotatus)

The Blue Eye Tang (Ctenochaetus binotatus), also called the Two Spot Bristletooth, is a calm, hard-working grazer with a bright blue ring around each eye and a black spot at the back of the dorsal and anal fins. Its comb-like bristle teeth scrape the thin film of algae and detritus off rock and glass all day, which makes it one of the more useful tangs for a reef. It is peaceful with most fish and easier going than many tangs, but it still grows to about 8.5 inches and needs real swimming room. Browse the rest of our saltwater fish and supplies.

Care Guide

• Tank size: starts in a 50 gallon (a 4 foot tank), plan on 70 gallons or more as it grows. Length matters more than height: tangs cruise the whole tank.
• Established tank: it grazes film algae and diatoms rather than hair algae, so it does best in a mature tank with plenty of rock to work over. A brand new, spotless tank leaves it hungry.
• Diet: a grazing herbivore. Offer dried seaweed on a clip most days, plus a quality marine pellet or flake with algae in it, and frozen spirulina mysis or brine as a treat. Feed small amounts two or three times a day; a thin tang is a hungry tang.
• Temperament: peaceful with most fish, but keep one bristletooth tang per tank. It will chase another Ctenochaetus (Kole, Tomini) and similar-shaped tangs.
• Water: 74 to 82°F, salinity 1.020 to 1.025, pH 8.1 to 8.4. Stable conditions and good flow keep it comfortable.
• Health: like all tangs it is prone to ich and lateral line erosion when stressed or underfed. Steady water quality, plenty of greens and a calm tank are the best prevention.

Specifications

Compatibility

A good fit with clownfish, gobies, blennies, cardinals, chromis, wrasses and dwarf angels, and safe with corals, shrimp, snails and crabs. It gets along with most tangs of a different shape in a large enough tank, and is often the calm tang that settles into an existing group.

Where it goes wrong: two bristletooth tangs (two Blue Eyes, or a Blue Eye with a Kole or Flame Fin Tomini) usually fight, and so can a tang added to a tank that is too small for both. If you plan more than one tang, add them at the same time into 100 gallons or more, choose different body shapes, and keep plenty of rockwork to break up sight lines.

Recommended Foods & Supplies

• Two Little Fishies SeaVeggies Green Seaweed or Rod's Food Three Weed Blend as daily greens
• Two Little Fishies VeggieMag to hold the seaweed in place
• Vitalis Marine Grazing Pellets or Hikari Seaweed Extreme for an algae-based staple
• Hikari Bio-Pure Frozen Spirulina Mysis as a treat a few times a week

FAQ

Will it eat my hair algae?
Not much. Bristletooth tangs comb the short film of algae and diatoms off surfaces. For hair algae a Scopas or Yellow Tang, or a cleanup crew, does more.

What size tank does it really need?
A 50 gallon, 4 foot tank is a fine start for a young fish. It grows to about 8.5 inches, so plan on 70 gallons or more long term, and bigger if it will share the tank with other tangs.

Is it reef safe?
Yes. It grazes rock and glass and leaves corals, clams, shrimp and snails alone.

Can I keep two?
Not two bristletooth tangs. It usually does fine with one tang of a different shape in 100 gallons or more when both are added together.

Why is its color dull or why does it look thin?
Usually diet or stress. Offer seaweed every day plus an algae pellet, keep the water stable, and give it time to settle in. Most look brighter and fuller within a few weeks.

Why the name Blue Eye?
The bright blue ring around each eye. The two black spots at the back of the dorsal and anal fins give it its other name, Two Spot Bristletooth.