Green Star Polyps

Green Star Polyps

Green Star Polyps - Metallic

Green Star Polyps are a common coral for beginners and still one of my personal favorites.  This coral encrusts to rock (or anything else it can touch) and once a large colony is established it resembles a wavy phosphorescent field of grass. The bright green splash of color waving in the current is a beautiful addition to the reef aquarium.

While the disposition of this coral is considered peaceful it is important to know that the coral should be placed so that the growth of the coral can be easily managed.  This coral grows quickly and many reef tanks have been quickly over taken.  Placing the corals on small “islands” of rock in the tank will keep them from spreading out of control.

GSP placed on "islands" so they do not take over the tank.

Common Names: Green Star Polyps (“GSP”)

Skill Level: Beginner

Classification: Soft Coral

Disposition:  Peaceful

Light Level: Moderate to High

Water Flow: Strong

Disposition: Peaceful

Water Conditions: 72-78° F, dKH 8-12, pH 8.1-8.4, sg 1.023-1.025




General Placement example for Green Star Polyps per lighting and water flow


Star Polyps contain zooxanthellae within their bodies to provide for the majority of their nutritional requirements through photosynthesis.  This basically means that they have the ability to get their food from the lights on your tank.  They can also benefit from weekly feedings of foods specifically designed for filter feeding invertebrates but it is not necessary. However, you may notice from time to time that when feeding your fish the GSP will trap small pieces of food with their tentacles.

Green Star Polyps grow by spreading a purple encrusting mat.  You will notice that GSP are an excellent indicator to your water quality.  Notice that your GSP is not growing as quickly as it used to? Check your pH and Alkalinity.  If your coral stays retracted into the purple mat through the “daylight” it’s possible you do not have enough water flow on the coral.   Lift the coral in front of the power head and blow off any debris you notice on the purple mat. It’s also possible to clean off the mat with a toothbrush.  This coral needs high flow to keep the mat clean.

Purple GSP Mat

Propagation of this coral is very easy.  The Purple mat can be peeled off the rock and super glued to another rock.  I usually start the peeling process with a flat head screw driver pushing it between the matt and the rock. Then once I have the mat raised up I slowly peel it off the rock with my fingers.  Once you have your section of the mat pulled off, simply place a few dabs of superglue on the new rock and glue the mat down onto it. It’s okay to have your coral out of the water for several minutes.  Once the glue is dry place your rock back into the tank.  Give your coral several days before you see full polyp extension.

When shopping for GSP you will notice there are several different color variations available. Some of the more popular colors are Metallic Green (neon green color) and Winter Green (Dark Green but longer flowing tentacles).  There are many other shades ranging from green to brown. I have also seen for sale a sort of purplish white although I have never personally owned one. Care is generally the same for all the different colors. You should choose a color that appeals the most to you and enhances your tank.

Interested in buying a Metallic Green frag? Buy Metallic Green Star Polyp frag

Interested in buying a Winter Green frag? Buy Winter Green Star Polyp frag

More Information: Additional Green Star Polyp Information

Need a simple fragging Kit? View fragging kit on amazon


12 thoughts on “Green Star Polyps

  1. Okay i have 1 ?? Do you need any Chemicals for this type of coral i have a 29g biocube in its my firs time doing this i have 3 marine tanks but ived never done reef pls help thank u .. Mike

    1. Hi Michael,
      As far as chemicals go I would say first the most important thing to make sure you have good water conditions that are stable. If you don’t have test kits for Alk , Nitrates, PH i would get those first and then branch into other test kits such as magnesium and calcium etc. These test kits will let you know if you have a need to add chemicals to your water such as buffer for PH. I hope this helps and please feel free to ask more questions if you have any.

  2. Hi I have gsp but it’s started lose colour and think some of the tentacles are going black.
    The tank is 50g led lighting all chems seem ok . The tank is 30″ deep tho would that matter gsp is about 6″ from bottom:

  3. Hi Tom,
    Fantastic site for the new-to-coral population!
    I’ve been in the hobby for ten years now and love the fact that there is always something new and fabulous to discover…Your site being one of those things:-)

    I have had GSP for over three years now and the colony just waxes and wanes. It was originally from a rock which had many hairy mushrooms on it. I have managed to give it plenty of room by removing half of the mushrooms, over a year ago, but it still is not living up to its characteristic “take over” behavior. Some might say this is a good thing, however, I would like it to create the island effect you have pictured here.

    I have mushrooms and Xenia which multiply like crazy, and have recently acquired a Hammer that has grown a new head in just three weeks! It is not within 6″ of the GSP though. ( I have checked hours after “lights out” for sweeper tentacles and found none.) I did notice that once I gave them ample flow they sprouted three polyps in a week though. Upon closer inspection I noticed brown algae on the mat so I brushed with a soft bristled toothbrush. Im wondering if there is anything else I can do to encourage the crazy growth I read about.

    Tank Specs: 55 gallon 48″Long; SSB; turbo and nassarius snails; skunk and peppermint cleaner; yellow tang; coral beauty; pseudochromis; 10 year old clown:-); grey banded brittle star; electric clam; paddle sponge- not doing well since addition of euphilia corals about three weeks ago ( I moved it from its happy place); purple sea blade- same as sponge; NPS gorgonian- RTN purchased this way hoping to bring it back who doesn’t love a “comeback story”?) and I head of candy cane frag.

    TIA for your help/suggestions/time’

    1. Hi Felicia,
      Thank you for your comment.
      If your gsp is not growing as fast as you might expect I would first look to see if your alkalinity levels are low. In my experience gsp will quickly soak up your alk. I’d it has stable alk levels then its growth will usually explode.
      Thanks and let me know how it goes!

  4. Hi, I live in the UK.
    I must add how much useful information your website has too offer, most impressive indeed.i have a 272litre reef aquarium, with mainly softie corals. What I find interesting regards to article on that if your GSP don’t open up during Daylight hours..offer more flow to them, I tried this but to no effect, I have now taken out my Tunze power head and Ramped up my return pump in the sump, to find that without the power head on all my GSP,s have now opened up completely. I wonder why to myself, could you offer some sort of explanation as to why?
    Many thanks.

  5. Hi Tom,
    Many thanks for your reply. My GSP,s are doing quite well since I reduced the flow,they are opening near to all.
    My Alk is between 8.6/9.3 my calcium is 450ppm Mag 1320 ppm my PH is constantly at 8.0 as I can’t seem to raise it, as it states GSP prefer PH levels above 8.1 could this be another reason that the GSP,s might not open entirely? My daylight hours are 6hours with 2hours sunset, 2 hours moonlight. Basically my hours of lighting are ten hours in all.
    Many thanks,

  6. I have a Metallic GSP and it has never opened in 2 weeks. It stays purple and is the size of my fist. All levels great. 75Gal tank. other animals are doing fine. I have move from the tank floor to the highest position to get greatest water flow. I have moved him back down now. He is laying on sand. I am going to put him on a rock today below and see if that does anything? Any suggestions?

Leave a Reply

Your email address will not be published. Required fields are marked *