Common Brittle Star (Ophiocoma wendtii): Care and Diet

You drop a pellet in after dark and a thin red arm comes out of a hole in the rock, wraps it, and pulls it back in. You had forgotten you even owned a brittle star. That is how a good one behaves: out of sight, working the parts of the rock nothing else reaches.

The common brittle star, Ophiocoma wendtii, lives on coral reefs from Bermuda to Brazil, including Florida and the Caribbean. Taxonomists have recently moved it to the genus Ophiomastix, so you will see Ophiomastix wendtii in newer references. It is the same animal. It is part of our Florida Keys clean up crew field guide.

Quick facts

What a brittle star eats

Brittle stars are scavengers. This one threads its arms into rockwork and under the edge of the sand and pulls out detritus and food that falls into crevices. That is the job the rest of the crew cannot do: snails stay on the surface, and hermits are too big for the narrow gaps.

In a very clean tank it can run short. A sinking pellet or a small piece of frozen food dropped near its hole once or twice a week keeps it fed. If you see it out in daylight, roaming, it is usually hungry.

The eyes it does not have

This species is famous among biologists. A 2001 study in Nature by Joanna Aizenberg and colleagues found that its skeleton carries tiny calcite lenses that appear to work as light sensors across the body. It also changes color: Reeflex describes it as deep crimson by day, fading to beige at night. That light sense is one reason it is so good at staying in shadow.

Not the green brittle star

The large green brittle star, Ophiarachna incrassata, is an Indo-Pacific animal with a reputation for catching small fish. The common brittle star is a different, smaller species with a scavenger’s diet. If you are buying a brittle star for a reef with small fish or shrimp, make sure of the species.

How many brittle stars per gallon

Our clean up crew calculator adds a brittle star only when you report detritus or leftover food, only in an established tank, and only from 40 gallons up. It adds one for every 60 gallons, rounded down, so one star covers 40 to 119 gallons and a second comes in at 120. A tank needs real detritus to support one.

Acclimation

Float the sealed bag for about 15 minutes to match temperature. Then drip tank water in slowly to match salinity, because invertebrates are sensitive to salinity swings. Never add the shipping water to your tank. Keep it under water when you move it.

Copper is toxic to brittle stars. Never add one to a tank that has had copper in it.

Lifespan, size and arm loss

Reeflex lists a maximum of about 7 inches across the arms. There is no reliable published lifespan. Brittle stars shed arms when grabbed or stressed and grow them back over time, so a star with one short arm is normal. A star losing several arms at once, or whose disc is breaking down, is reacting to water quality. Test salinity first.

How we find them in the Florida Keys

Common brittle stars live on Florida and Caribbean reefs in rubble, under ledges and in reef crevices. By day you only find them by turning rubble. We collect them by hand under our Florida certificate and condition them in our Key West systems before they ship.

FAQ

The Underwater Gardener is a reef store in Key West, Florida. Our Florida Keys clean up crew is collected by our team under Florida certificate #AQ0254072 and conditioned in our Key West systems before it ships. Livestock ships UPS Next Day Air on Tuesdays and Wednesdays.