Pachyclavularia

Pachyclavularia, commonly sold as Green Star Polyps (GSP), is often confused with Briareum — both are sold under the GSP name and share a nearly identical appearance of bright green star-shaped polyps emerging from a purple encrusting mat. The care requirements are essentially identical regardless of which genus you actually have. Place them under moderate PAR (75–200 PAR) with moderate flow in virtually any position in the tank — they are extraordinarily adaptable. Standard reef parameters are fine: alkalinity 7.5–9 dKH, calcium 400–440 ppm, and temperature 25–27°C. GSP tolerate a remarkably wide range of lighting from low to high.

The defining characteristic of GSP is their aggressive growth rate. They are one of the fastest-encrusting corals in the hobby and will cover any surface they can reach — rockwork, glass, equipment, overflow boxes, and even other corals. Many Australian reefers deliberately use GSP to cover the back wall of their tank, creating a stunning living green backdrop. To prevent unwanted spread, isolate GSP on separate rock islands surrounded by sand, or mount them on removable structures like magnetic frag racks. Regular pruning by peeling back the mat is necessary to keep them contained.

Fragging is trivially easy — peel or cut sections of the purple mat and glue them to any surface. They will begin spreading within days. GSP polyps retract quickly when disturbed, revealing the purple mat underneath, and will re-emerge within hours once conditions settle. This retraction behaviour makes them a useful visual indicator of water quality changes. GSP are among the cheapest and most abundant corals in Australia, freely available at every frag swap and coral retailer. They are the perfect first coral for any new Aussie reef tank.