Green Brittle Star

Ophiarachna incrassata, the green brittle star, is a large (to roughly 25–30 cm arm span) nocturnal Indo-Pacific brittle star prized for its vivid green-and-yellow colouring. Unlike most "reef cleanup" brittle stars, it is a documented active predator: it props its oral disc above the substrate, waits for a fish or shrimp to pass beneath, then drops and tents its arms around the prey and pulls it in. It targets small fish (especially bottom-sleepers), ornamental shrimp and other motile invertebrates, but it does not eat coral tissue, so it remains reef-safe for sessile life even though it is not tankmate-safe. House it only with fish and inverts too large for it to subdue.