Star Polyps and Briareum: The Ground Cover Corals That Do the Work For You
Posted by Gallery Aquatica on
Star polyps and Briareum are two of the most forgiving soft corals in the hobby, and they get recommended constantly for good reason. Both grow a fleshy mat or encrusting base that spreads outward, sending up small feathery polyps that sway in even modest flow. They are not fussy about light, they tolerate a wide swing in water quality better than most SPS, and they grow fast enough that a small frag can cover a decent patch of rock within a few months.
Green star polyps, usually shortened to GSP, and its close relative Briareum (sometimes called star polyps too, which causes a lot of confusion at the shop counter) are technically different genera but get kept and sold in similar ways. GSP tends to form a bright mat with polyps in green, yellow or combinations, while Briareum, like the choc mint variety, often has a darker purple-brown or grey encrusting base with polyps that can be green, cream or a mix. Both belong in the same conversation because they behave the same way in a tank: fast, hardy, and happy to spread.
Why beginners gravitate toward them
Most soft corals in this group will tolerate PAR readings anywhere from about 50 to 150, which covers a huge range of lighting setups, from an ageing T5 fixture to a modern LED run at moderate intensity. They are not demanding about trace elements either. Standard reef parameters, salinity around 1.025 to 1.026, temperature 24 to 26 degrees, alkalinity in the 7 to 9 dKH range, are all they need. Flow should be moderate rather than blasting, enough to keep the polyps moving and prevent detritus from settling on the mat.
They also feed themselves largely through photosynthesis, so target feeding is optional. If you want to encourage faster growth you can dose a broad-spectrum coral food occasionally, and products from our coral food range work fine for this, but it is not essential the way it is for large polyp stony corals or clams.
The containment problem
The reason experienced keepers give star polyps and Briareum a slightly wary reputation is that they do not know when to stop. Left directly on display rock, a healthy colony will creep across the surface, over rockwork joins, and eventually into contact with neighbouring corals. GSP in particular can overgrow slower growing soft corals and even encrust onto the base of LPS if given the chance. Once established over a large area, removing it without damaging the rock underneath is a genuinely fiddly job involving a lot of scraping and a fair bit of patience.
How to keep them in their place
The fix is straightforward: never mount star polyps or Briareum directly onto your main display rock. Instead, glue the frag onto a ceramic tile, a flat piece of dead coral skeleton, or an isolated rock island sitting in its own dish or a small acrylic frag stand. Leave a visible gap of open sand or bare glass between the mounting surface and any other rockwork. The coral will happily fill its allotted tile or slab and then stop, because it cannot bridge open water on its own. Some keepers deliberately use this trait to create a low, colourful carpet at the front of the tank or along a sump baffle, using the growth as a design feature rather than fighting it.
A dab of cyanoacrylate gel from our glue and adhesives selection is the easiest way to fix a new frag in place, and a pair of fine scissors makes trimming overgrowth simple if a colony starts creeping toward the tile edge. Trimmed pieces can be re-mounted as new frags, which is part of why these corals move through the hobby so freely.
Star polyps and Briareum are a genuinely good starting point for a first soft coral tank, cheap on the eye if not always on space, colourful under almost any lighting, and forgiving of the mistakes new reefers tend to make. Because we work with local aquaculturists and change colonies regularly, the exact colour morphs on hand shift over time, so check out our stock list for soft coral to see what frags of GSP and Briareum are currently on the list before you plan your next tile.