Green star polyps in reef tank

Green Star Polyps Coral Care

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 close up

Let’s dive a bit deeper into what it takes to care for green star polyps in your home aquarium.

Table of contents

This article was re-written and updated in October 2020

Quick care guide facts

  • Scientific Name: Pachyclavularia violacea
  • Common Names: Green star polyps or GSP
  • Care Level: Beginner/easy
  • Aggression Level: Peaceful, but it will try to grow over everything in reach
  • Color: Green polyps, white center, purple mat or stolon
  • Coral Group: Soft corals
  • Growth Form: Encrusting
  • Key Nutrients: Nothing special to report here
  • Temperature: 78-82 degrees Fahrenheit (25.5-27.8 C). Mine did survive a several day power failure, the temperature in the 50s (F)
  • pH: 8.2
  • Alkalinity: 8-12
  • Calcium: 400 ppm
  • Salinity(measured as specific gravity): 1.025
  • Ammonia, nitrates, and nitrites = 0

Green star polyps in reef tank

Ideal conditions for green star polyp coral (GSP)

Standard aquarium water parameters are perfect for these corals. Keep your water temperature stable, at around 78 degrees F. Use a high-quality reef salt mix, like Instant Ocean, and maintain a specific gravity around 1.025. Top off the tank with moderate-to-strong LED lights and at least low-to-moderate water flow, and after a few months, you’ll have to trim your green star polyps back to keep them from growing over everything.

It is worth mentioning that the ideal conditions listed above are ideal for the majority of soft coral species. 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 in a saltwater aquarium

GSP corals are not fussy and will likely thrive wherever you put them, as long as you have met the minimum conditions required: adequate light, water flow, and water quality.

However, 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.

I’m convinced that the main reason for this cyclical growth pattern is related to the total amount of light. If I increased the light around the periphery of my tank, the growth could undoubtedly continue to even greater amounts.

green star polyps on live rock

Feeding and nutritional requirements

GSP corals are partially 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.

If you are new to the hobby, or if your green star polyp colony is one of the first in a new tank, you may want to consider target feeding, to accelerate the growth and help fill in some of the empty substrates with living corals. But please keep in mind, this is already a naturally fast-growing coral, which may colonize more surface area than you had already planned.

Do you feed green star polyps?

Yes, you should feed your green star polyps. All corals are animals. This can sometimes be forgotten since we focus so much on having the right amount of light, but it is generally best to feed your corals.

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

Sorry that the image quality is so grainy. I took these photos in my own tank, without any special magnification gear. Literally just using the physical and digital zoom. Which also provides some context to the relative size of the serrations.

At the base of the colony, each of the polyps is attached to each other by a thick, rubbery purple matt, called a stolon.

Lighting requirements for the bulletproof green star polyps coral

You may hear the term, “bulletproof coral” used to describe some of the hardiest corals available in the hobby. It is certainly a curious phrase–and of course, is an exaggeration.

Lighting requirements are fairly straightforward for this hardy, beginner soft coral.

  1. Avoid extremes (high and low intensity) in the lighting
  2. Acclimate the coral to your tank if you do have powerful LED aquarium lights
  3. Do not move the coral around a lot to different parts of your tank (changing light and water flow).

Long tentacle green star polyps in strong current

The polyps do appear most aesthetically pleasing with some blue or actinic lighting to help make the green polyps pop, but they do not require this to grow in your tank.

Troubleshooting: Green star polyps closed or not opening in tank

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)
  • when salinity is off (like when I haven’t topped off with fresh water in TOO LONG)

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 in tank with GSP (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 for GSP aquarium care

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

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) and is growing out on the side-wall.

green star polyp care growing on back wall of aquarium

Note the polyps growing up the back wall and side of the tank

Each year in my tank, the GSP 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 coral 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 polyps attempt to grow forward over every surface, including rocks, other corals, and aquarium glass.

Check out this short video all about green star polyps

Are green star polyps poisonous?

Green star polyps are not poisonous in the same way that zoanthid polyps are poisonous. Some palythoa zoanthid species have a toxic chemical called Palytoxin that they release when stressed. Learn more about palytoxin (not associated with green star polyps) here.

Hopefully, this goes without saying, but your GSP is not for human consumption, regardless of what I just wrote regarding palytoxin. Finally, just because they don’t have palytoxin doesn’t mean they won’t damage neighboring corals as they grow. They will. Hope that helps.

Natural range for Pachyclavularia violacea.

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).

Where to find this soft coral for sale

GSP corals 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 soft 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:

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, and Reef Journal

green star polyp GSP coral care guide pinterest pin


  1. I have a lot of corals in the tank that requires feeding once every other day . I use a pump to blow over excess nutrients after 5 hours later but a lot of the times, algae will take over my star polyps in the end.

    1. Author

      Stephen, thanks for the comment. I’m sorry that I don’t totally understand–would you mind re-commenting, so I can be of better help (if possible)? Are you having problems growing green star polyps (due to algae growing faster?)

  2. New to salt aquaria. Starting a 32 gal bio cube and got some star polyps today. I think they look amazing in photos. I look forward to when mine fill out. I know common and easy things can become boring in hobbies. But I would like these regardless of rarity or price. Glad they are easy and inexpensive.

    1. Author

      Jim, these are great corals. Typically easy to keep. I agree, stunning to see that vibrant green matt. Also agree that if they were harder to keep/frag/grow or rarer, they’d sell for a fortune. they’re Awesome.

  3. Any advise for little or no opening of my GSP. All my other corals are doing great, zoas, hammers, Gonis.

    1. Author

      I have observed that the entire colony will close up whenever something disturbs any part attached to the mat–is anything picking at the coral? Also, can you please share a little more information? How long has this been going on? Is it a change from before where they were open or have they ‘never’ opened up in your tank? Any changes to water parameters at all? What type of light intensity are they under? Those are a few things to explore. Hoping it perks up for you soon. thx.

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