green star polyps

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 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 aesthetically 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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  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. My Green Star was growing well for about 3 Years, then suddenly died requiring a massive water change, but upon picking the dead ‘foot’ I found a White Bell shaped jelly like (what) growing on the underside, reminded me of Fungi but do they grow in a Marine environment? You tell me!!

    1. Author

      Shirley, thanks for the comment. Sorry to hear about your GSP. What a bummer. Not sure what the jelly was and whether it was the cause of the issue or just feeding off the dead stuff…ugh. that must have been frustrating.

  3. Yes well despite having kept Marines for many (40)+ Years, one still gets fooled at times these growths were transparent/milky white, I now realise they are embryonic mushroom corals these had no Colour because they were growing in the Dark, it’s one of the things I love about keeping Corals, you never know what to expect, having had Jellyfish appear, various Cucumbers, Clams, etc, from so called ‘cured’ Rock, I now want to set up a 3ft tank separate from the others and fill it with ‘uncured’ Rock and see what happens over a Year or so. Shirl

    1. Author

      Shirl, thanks for the comments!! I think the ‘you never know what to expect’ aspect of this hobby is what I like most! I absolutely love it when I find new, unexpected (non-harmful) inverts).

      Thanks, also for commenting and adding to the discussion, it gets lonely here, I appreciate all our contributions.


  4. Really love these beautiful corals. A quick question from a relative newbie – are there different varieties of GSP? We have just bought a mushroom colony with what appear to be small areas of a very bright green GSP, but it looks very different from our GSP colonies we already have. Smaller and much brighter in colour. Many thanks.

    1. Author

      Hi Leslie,

      Thanks for the question. Yes, there are certainly going to be different varieties and even species available within the genus that are going to be substantially similar to care for but look a bit different.

      Sounds like you got a ‘free’ hitchhiker there. Enjoy!!

  5. Newbie here. Got my first GSP and they are not green 🙁 What could the problem be?

    1. Author

      Hi Pricilla and thanks for the question. Due to my delay in getting back to you (very sorry about that). Here is my first conclusion/line of thinking: Green star polyps have a complex and fascinating anatomy/body structure, but two of the most prominent features we see are the green polyps (when extended) and the purple stolon or mat that the polyps attach to. When the polyps or stolon are damaged, threatened or even ‘unhappy’, the polyps will retract and all you will see is the purple mat with a bunch of wart-like buds that are the retracted polyps.

      So my guess is that something is either physically or chemically distressing the coral, so you are only looking at the mat and not the polyps. As such, the course of action would be to identify the offender and remove it or improve the conditions. Check water parameters, water flow, look for a fish nibbling on the polyps, anything that would be stressing it. Also, if you just added a new coral either after a long trip thru shipping or added to a brand new tank, this ‘unhappiness’ you see can just be related to cumulative stress and an adjusting period to your new tank conditions.

      Apologies that this note is so late. It got hung up between my personal delays and a Spam filter (there are lots of spam comments that come in thru comments, unfortunately).

      Since the GSP is such a hardy coral, I am hopeful that your colony has adjusted to life in your new tank and is thriving.

  6. Enjoyed the post but have a few questions. We’ve had a very nice GSP for about 2 months and it was in excellent condition. Suddenly we noticed some die off (we think) in different areas of the piece. We have what we think is both green and brown/red alge which grows rapidly (within days of maintence). Test parameters show a slight amount of nirate and a really high phosthate (.9) which we began treating several days ago. Any suggestions?

    1. Author

      Hi Bill,

      Sorry to hear about the challenges there. I know these things can be frustrating. A couple of thoughts. Can you make sure you have appropriate lighting for the GSP? A healthy GSP with sufficient light/nutrients grows aggressively. The die-out is possibly a combination of the problem algae you see and possibly (unsure about the light situation) insufficient lighting/nutrition for the GSP. I only share that b/c I see growth/retraction with my GSP depending on where my overhead lights are–when I’ve moved them (inches) I’ve noticed different growth patterns between the area that got light and lost light and decay in the middle, with some algae growth was seen in those areas that ‘got less’ light. Also, clean your lid or anything that might be dampening the light above the GSP.

      Now onto your original conclusion, re: algae. Try to keep the stolon (purple mat) free from debris/detritus/algae by ‘blowing out’ any detritus (with a pump or turkey baster) and physically remove any algae for a few days (or longer, if you can). After some spot cleaning like that (blowing water and spot removal of stuff), if you can redirect powerheads to make sure you have good enough flow to keep stuff from settling on them, that’s best-case (and lowest maintenance for you).

      Then would encourage you to try and solve the phosphate mystery…remove it (water changes, phosban) and prevent it (identify the source and stop it from getting in).

      By doing all those things you will: remove an ‘easy’ place for the algae to grow (detritus) and the food/fertilizer boosting growth (phosphate) and encourage the happy healthy growth of the GSP (light + flow) which in turn should make a healthy coral capable of fending off the algae.

      I hope that helps and isn’t more than you bargained for.

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