Thorn Coral

About

Thorn coral (Stylocoeniella guentheri) is one of those species that rewards a closer look. Its colonies grow as flat, encrusting sheets with a knobby, almost rough-hewn surface texture created by the small but characteristic spiny projections, called styles, covering the coenosteum between corallites. The individual polyps sit flush with that surface rather than protruding, and are widely spaced, giving the colony a sparse, understated look compared to many reef-building corals. Coloration tends toward greenish-brown, ranging from pale to quite dark, sometimes mottled, and the polyps are typically white. Found across a wide sweep of the Indo-Pacific, this coral occupies reef environments from shallow water down to around 50 meters, and its broad latitudinal range means it tolerates more temperature variation than many tropical species. Large colonies over half a meter across tend to appear more commonly at higher latitudes. In the aquarium, thorn coral is considered an advanced-level keep. It wants intense lighting and vigorous water movement to reflect the wave-swept reef conditions it comes from. It is reef safe, posing no particular threat to neighbors, but meeting its flow and light demands consistently is not always straightforward, so this one is better suited to experienced reefers with dialed-in systems.