Saltwater Aquarium Blog

soft coral care guide for reef aquarium

Introduction to Green Star Polyps Coral Care

Green star polyps are an excellent beginner soft coral and might be the ideal first coral choice because they are:

  • extremely hardy
  • easy to care for
  • tolerant of a range of water conditions
  • fast-growing
  • don’t need a lot of light to grow

Green star polyps will grow on just about any aquarium surface, including the aquarium glass, plastic, live rock, and even other corals. I have witnessed all three behaviors directly in my own tanks. The image below was taken in my display tank a few years ago.

Notice how the coral is growing up the back wall (that’s where the overflow is) an is growing out on the side-wall.

green star polyp care

Each year in my tank, the coral seems to go through a series of growth and recession cycles. My tank is a 92-gallon bowfront aquarium.

There is a central, massive GSP colony covering most of the back wall of the aquarium and the live rock in the back — and the coral grows outward, on the side glass in both directions.

The GSP attempts to grow forward over every surface, including rocks, other corals and aquarium glass.

Check out this short video

Natural range

Green star polyps are native to the rubble areas of reefs and lagoons and are often found with Xenia and clavularia, commonly in areas that are typically nutrient-rich with low water flow (Borneman 2001).

Ideal conditions

Standard aquarium water parameters are perfect for these corals. Water temperatures around 78 degrees F and a specific gravity around 1.025, combined with moderate-to-high light and moderate to low water flow are all the special care that this coral need.

No special care is particularly required to keep these corals, beyond the typical husbandry skills required for caring for any coral species.

GSP coral placement

These are not fussy corals and will likely thrive wherever you put them, but the best placement for green star polyps in a reef tank is in an area with moderate flow and lighting. As shown in one of the images above, the colony in my tank spreads out along the back wall and side wall aquarium glass, but it tends to expand and retract over time, but the area most directly in the flow and under the lights tends to thrive all the time.


GSP’s are photosynthetic and get nutrition from their symbiotic zooxanthellae. They also presumably absorb nutrients from the water column, as well, and have historically done well in systems with well-fed fish. Their polyps will also capture and pull in food particles that they catch in the water column. While target-feeding will likely increase growth rates, this coral grows quite well under normal reef aquarium conditions without supplemental feeding.

Taxonomy, morphology and body structure

The scientific name for Green Star Polyps (GSP) is Pachyclavularia violacea. Other names are starburst polyp, star polyps, and daisy polyps. According to Borneman, in Aquarium Corals, green star polyps were one time thought to be Clavularia viridis, but this is not correct. They are octocorallians–which means they belong to the class (subclass) of corals that have 8 tentacles on every polyp.

GSP polyps have 8 tentacles

They are also part of the Alcyonacea order, which means they are part of the same part of the coral family tree as the leather corals. Each tentacle has a serrated appearance to it, when examined close-up, as can be seen in the next image, below.

GSP tentacle up close

The polyps are attached to each other by a thick, rubbery purple matt, called a stolon.

Lighting requirements for this bulletproof coral

Lighting requirements are fairly straightforward for this hardy, beginner soft coral. Avoid extremes (high and low intensity) in the lighting and acclimate the coral to your tank if you do have powerful LED aquarium lights.

The polyps do appear most aesthestically pleasing with some blue or actinic lighting to help make the green polyps pop.

Green star polyps closed or not opening

When disturbed, the polyps can fully retract into the stolon, for protection.

This tends to happen:

  • in response to cutting, fragging or trimming back the coral
  • at night time
  • when stressed (like during power failures)

I’ve observed that the GSP polyps exhibit a shared response depending on the severity of the disruption. Minor disturbances tend to only cause a few polyps local to the disturbance to retract, but if I scrape-away stolon and polyps covering up the slits in the overflow (a more dramatic disturbance), polyps across the entire colony will retract.

The coral looks like this, with its polyps retracted:


note the retracted polyps (little purple bumps) from this coral


How to frag green star polyps

Green star polyps (GSP) are one of the easiest corals to frag since they are an encrusting species that will grow on just about any substrate. If you line up a few pieces of live rock rubble touching the rock the green star polyps (GSP) are on, the polyps will grow out from the base rock and encrust the rubble.

Free up the frags by cutting the purple mat, called a stolon, with a knife or scissors.

If you want to learn how to frag green star polyps or any other coral, download my definitive guide.

Compatibility with Pachyclavularia violacea

Unlike some other coral species, green star polyps do not have stinging tentacles, called nematocysts, so they are relatively peaceful and compatible with other coral species. Green star polyps grow quickly and encrust on anything within reach–including your other corals.

So if you want to keep green star polyps with other coral species, you need to maintain physical separation between the rocks the GSP are growing on and neighboring rocks or the green star polyps will eventually take over all the connected rocks.

Special considerations

Green star polyps are a fantastic beginner coral because they grow so fast and adapt well to life inside a home aquarium. Because they will grow on just about any substrate, they are a great coral to get creative with, in your tank. GSPs will grow up the aquarium glass or overflow, they can encrust wires or tubes, so if you can turn any surface inside your aquarium into a fuzzy, living mat. In my display tank, my green star polyps have grown up the back wall of the tank (technically an overflow). Where can you grow them?

green star polyps growing

these green star polyps are growing over an aiptasia and zoanthids

Where to find this soft coral for sale

GSPs are an aquarium staple and are available at most local and online stores. Considering how well they grow and can be fragged, I’m always a bit surprised by the price tag at some stores. Especially since anyone growing this coral would likely give away a frag for just a few dollars. But I know operating a local fish store is a tough business. I suspect these popular corals help keep the lights on.

Here are two places to shop for them online:


green star polyps

A quick question for you

What do you think about the green star polyp? Please leave a comment below.

To learn more about caring for green star polyps in your reef tank, watch this video here:

How to grow and frag green star polyps

Written by Albert B. Ulrich III–author of The Reef Aquarium Series of books:  The New Saltwater Aquarium Guide, How to Frag Corals, 107 Tips for the Marine Reef Aquarium.

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