The green brittle star is a large, bright green starfish relative with a central disc up to 4 cm across and banded arms that span 40 cm or more. It is one of the hardiest echinoderms you can keep and an efficient scavenger.
Ophiarachna incrassata has a dark side: it is an active predator that catches small fish at night. Choose its tank mates with care.
Where green brittle stars come from
The species lives in the Indo-Pacific, from the Philippines and Indonesia to northern Australia, on shallow reefs and among rubble.
Appearance and behaviour
Brittle stars move quickly for an echinoderm, using their flexible arms rather than tube feet. They hide under rocks by day, with only an arm or two showing, and come out at night or when they smell food.
To catch fish, a green brittle star waits with its arms raised to form a cave, then wraps them around any small fish that shelters there.
Tank setup
A tank of at least 200 litres with plenty of live rock and caves suits one. Keep only one per tank, since they can fight.
Water parameters
- Temperature: 24–27°C
- pH: 8.1–8.4
- Specific gravity: 1.023–1.026
Like all echinoderms, they need stable salinity and should be drip acclimated slowly. They do not tolerate copper.
Feeding
Feed small pieces of shrimp, clam, mysis and fish a few times a week, placing food near the arms. A well-fed brittle star is less likely to hunt fish.
Tank mates
Keep with fish larger than 7–10 cm, such as tangs, angelfish and larger wrasses. Avoid gobies, firefish, small blennies and shrimp. Corals are safe.
Breeding
Green brittle stars spawn into the water, but they do not reproduce in home aquariums.
Common problems and lifespan
Disappearing small fish are the main issue. They can regrow lost arms. With good care they live five years or more.
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