Thorn Coral

About

Thorn coral (Stylocoeniella armata) is a compact encrusting species that grows as a low, spreading sheet across hard substrate in shallow reef environments. What sets it apart from other encrusting corals is its distinctive surface texture: the corallites sit well apart from one another, each surrounded by a raised coenosteum that gives the colony a rough, almost spiny appearance. Hence the common name. The septa within each corallite run in two roughly equal cycles, and the overall structure has a neatly geometric quality when viewed up close. Coloration varies quite a bit, ranging from deep or bright red through various shades of brown to green, so individual colonies can look quite different from one another. In the wild, this species occupies shallow, well-lit reef zones where water movement tends to be strong. Recreating those conditions in the aquarium is non-negotiable. This coral does not respond well to low flow or subdued lighting, and is best suited to experienced reefers who can maintain consistently stable, high-quality water. It is reef safe and poses no threat to neighboring corals through sweeper tentacles, but like most encrusting species it will slowly colonize surrounding rock, so give it room to spread without overrunning more delicate neighbors.