Green Star Polyp Appearance, Care and Tank MatesGreen star polyps are very pleasant to keep since they add color and movement to your tank at home.

Benefits of keeping them in your aquarium are numerous, such as being inexpensive and also hard, this means you don’t have to go through much to give them proper care. Read more to find out about green star polyps

What are Green Star Polyps?

Green Star Polyps, scientifically known as Pachyclavularia violacea, is a soft coral species that can grow on most surfaces, including glass, rock, plastic, and even over coral.  Learn more by reading this article, to place some in your own tank.

They are commonly referred to as GSPs for short, but they are also known as star polyps, starburst polyps, and daisy polyps. This coral is the best choice for beginner aquarists as it quickly fills up empty space and also adds movement and flow to the tank.


Let’s see out some quick facts about the green star polyps to get to know them better-

Scientific name Pachyclavularia violacea
Other names Daisy polyps, Starburst polyps, Star polyps, Purple Mat polyps
Care level Beginner
Size 2 inches diameter
Temperature 78F
Calcium 420 to 500
Salinity 1.020 to 1.026
Lighting Moderate to high
Water flow Low to moderate
Placement Any
Growth rate Extremely fast
Water hardness 8.1 to 8.4 
Colours Fluorescent neon, brown,

Wintergreen, purplish-white

Where Green Star Polyps Are Found

The green star polyps grow profusely in the shallow tropical waters of the Indo-Pacific. They are found in the rubble areas of lagoons and reefs at a depth of about 62 feet in the ocean. Their origins are in Fiji, Tonga, the Solomon Islands, and the Great Barrier Reef. In some of these places, they may have been aquacultured easily.

Due to these origins, there was a time when GSP was mistaken for Clavularia viridis. However, the conception turned out wrong since they’re octocorallia with eight tentacles on each polyp. Green star polyps fall under the Alcyonacea order, which is the same coral family as the leather corals.


They have eight feathery retractable tentacles. Each of the tentacles of these corals has a serrated appearance. That’s why they are often known as “Daisy polyps.” These polyps are attached to each other through a thick and purple rubbery mat called the stolon.

Green star polyps are esthetically pleasing to look at. Their bodies are usually bright fluorescent green with a band of yellow or white around the outside of the central oral disk. These neon green star polyps can come together to increase the vibrancy of your tank many times. 

Sometimes they also come in a color called “Wintergreen,” which makes their long, flowing tentacles appear dark green. In some cases, they might even be brown or purplish white.

Green Star Polyps Care

Green star polyps are often called bulletproof polyps because they are very hardy. It’s fairly easy to take care of them, so they are always recommended to those who are just starting out with raising corals. However, that does not mean you should just chill and not work on all of their important requirements.

From lighting to water flow, green star polyps are very sensitive, so you will have to work hard to keep their environment stable. If you don’t manage to do that, they will retract into their stolons, and it will be difficult to get them to open up again.


While setting up a tank for your green star polyps, there isn’t much you have to do except ensure the best lighting. These are often called the hardiest corals available in the hobby, but the claim is quite exaggerated. They are still the best soft corals for a beginner, so the green star polyps lighting, requirements are nothing too complicated.

First of all, avoid the extremities when it comes to green star polyps lighting, in other words, don’t make the intensity of the light too high or too low. You should acclimate the coral to your tank only if you have powerful LED lights in place. They appear the most gorgeous when under blue or actinic lighting. The green polyps will pop especially well with this color.

However, any other color will do as well. Just make sure not to move the coral around to different parts of the tank. In short, it will change both the light and water conditions, which will affect their health.


A lot of aquarists, especially those who are new to the hobby, think that corals don’t have to be fed. But that is a wrong conception to own. All corals are animals as well, and they need food just like any other animal would. It’s easy to forget that since a lot of attention goes into other factors while raising corals in a tank, it’s usually best to feed them.

Feeding green star polyps is not a hassle, since, GSP corals are partially photosynthetic. They get their nutrients from their symbiotic zooxanthellae. They can also absorb nutrients from the water column by pulling in and capturing the food particles floating there. 

That’s why, historically speaking, green star polyps thrive best in systems with fish that are fed properly. This coral grows healthily under normal reef aquarium conditions. Noting that, for the new tank owner, the colony is the first thing in a new tank, so you can consider target feeding.

Target feeding has the potential to accelerate the rate of growth of the corals, which will help fill up the empty spaces of the substrate with living corals. 

However, remember that green polyp corals naturally grow very fast. Hence, while they will spread fast, they might also end up colonizing more surface area than you had planned. This can lead to several complications for other fish in the tank. So even with target feeding, there should be a limit.

Growth Rate

One of the main reasons why green star polyps are always recommended for beginners is that they grow fast and easily. Having in mind how they are encrusting species, that can grow on just about any type of substrate, no matter where you place them, they will spread easily. All you have to do is ensure that they get the right amount of light.

The more lights, the faster they will grow. While some aquarists prefer that for their tanks, others may find it invasive. Especially if they have other fish in the tank as well. In fact, due to their slightly aggressive temperament, they can even grow over other corals. 

As the growth gets too much after a point, you should trim when it’s time to prevent them from growing over just about everything in the tank. Otherwise, it might start affecting other fish in the tank. On the other hand, if it is not growing as quickly as it once did, it might be because the pH and alkalinity of the water are slightly off.


Now that you’re done preparing the tank, it’s time to place the green star polyps in it. They are very adaptable creatures, so they will thrive more or less wherever you put them. You won’t have to go out of your way to create the perfect spot for them. 

Nevertheless, there are still some minimum requirements that you have to meet for their wellbeing. These requirements include adequate lighting, perfect water flow, and good water quality. You should find the best spot for your green star polyps even after meeting these requirements. 

For a reef tank, the best spot would be an area with moderate flow and lighting, specifically, the area directly in the flow and under the lights. Your green star polyps will thrive the most in this spot and show their prettiest colors. 

Coral colonies tend to spread out along the back and sidewalls of the aquarium glass, and sometimes they retract, and sometimes they expand. hence, if you keep them in that kind of area, they will get the right amount of light and the appropriate water flow, which will help with their balanced growth.

On the other hand, if the placement is wrong, like being too close to the lighting or in an area with extreme currents, then the polyps might get damaged and retract to their stolons. It might take them several months to open back up. Therefore, where you put the frags of your polyps is an important matter.

Water Conditions

Luckily for you, these corals can do well in the standard aquarium water parameters. Noting that, it’s crucial that the parameters are stable and don’t fluctuate too much. Hence, you have to monitor the parameters with a testing kit on a regular basis, especially after a water change.

Green star polyps are saltwater corals, so you can use a high-quality reef salt mix to create the perfect water for them. Instant Ocean is a popular salt mix that you can try out for the tank. Keep the temperature stable at around 78F and the specific gravity at around 1.025.

Following this, come both the lighting and water flow. Since lighting has an effect on the growth rate of the corals, it is crucial to keep it in the range of moderate to strong. The lights should be LED for the healthy growth of the polyps.

The water flow should be within a low to moderate level, as too much water flow can be harmful. The same water conditions will apply to most soft corals.

Fragging And Propagation

Green star polyps are one of the easiest corals to frag, thanks to their encrusting type of coral. These corals can grow on almost any substrate. Therefore, all you have to do is line up a few pieces of live rock rubble along the surface of the coral. 

After which, the green star polyps will begin to grow out from the base of the rock, as a result, they will encrust the newly found surface very soon. When the latter happens, you can just free up the frags by cutting the stolon with a knife or a pair of scissors.

For propagation, you have to peel small frags off the mat from one rock first. Cut it with a flathead screwdriver, then slowly peel the coral away from the rock with your fingers. Once you have freed some of them, you can use small blobs of super glue to attach each frag to another rock or surface. Replace the rock with its coral frag back into the tank after the glue has dried.

Why Do Green Start Polyps Not Open?

Green Star Polyp Care Guide for Beginners

Sometimes green star polyps fully retract into their stolons for protection. There are many reasons why green star polyps will not open, and a common reason is a misplacement of the coral, which can alone create multiple issues by causing the polyps to be retracted. 

It can also be due to inappropriate lighting or a prolonged lack of lighting due to power failures. Algae in the tank, on the other hand, wrong water parameters, heavy water flow, and basically anything that can make them uncomfortable are also caused. The salinity will be off if you haven’t topped off the tank with fresh water for too long. This can also make green star polyps closed.

Moreover, cutting, fragging, or trimming back the coral can also stress them out. If there are pests in the tank, or the corals are disturbed by fish and critters, it can also be a cause for the retraction. Overall, any of these disruptions can cause them to acclimate and feel stressed.

As a response, they will retract to protect themselves. If the disruption is minor, you might only see a few of the polyps near the source retract. In contrast, a more dramatic disturbance, like covering up slits in the overflow, can cause the entire colony to retract.

How to Solve?

So if you see your green star polyps not opening, you first have to identify the cause and then work on it. There are some examples to consider:

  • Placement: Since placement is usually the biggest reason, you should move them to the right spot in the tank for them to open back up. The right spot is where they can get the right amount of lighting, the required flow of water, and the appropriate parameters.
  • Fish or critters: You might have critters like hermit crabs walking over the coral all the time. If the colony has a lot of algae on the top, the critters and some fish may be on the corals all the time for feeding purposes. 

Opening the polyps

If there is algae growth on the polyps, first, you can use a turkey blaster on them. This will make sure the polyps are fully closed before you lightly clean off the algae with a soft-bristled toothbrush. Since the GSP mat is hardy, your corals will be fine unless you brush too hard.

  • High salinity: It’s not difficult to detect high salinity and then bring it back under control. You will need a refractometer to measure that. It’s not recommended that you use other types of cheap tools that can be found at a big box fish store.
  • Acclimation: An important thing to keep in mind is the fact that corals in a new environment will take some time to open up. For some, it might only take a few hours; for others, it may take several days. Noting that they do it out of stress, and it’s very natural. Hence, if there have been environmental changes in the tank recently, give your corals more time to open up.

If you have received a frag that has been established on a plug for a while, then it should open up pretty soon if everything else is okay. However, if you get a piece that was just cut from a bigger colony, it might take longer to open up. Due to these changes in the water parameters, it will take them a while to acclimate.

Nevertheless, at some point, you have to determine whether they have already had enough time to acclimate. If it’s been a long time since green star polyps closed, then there is definitely some other issue that you need to identify.


Green star polyps can add both color and movement to your home aquarium. They are not only inexpensive but also hardy, so you won’t have to go through much to care for them. If you have decided to get some frags for your tank, go through these important points once more:

  • Green star polyps are saltwater species of corals that can grow on most types of substrates.
  • Though they can get enough nutrients through their zooxanthellae, spot feeding is good for their growth.
  • You should only use moderate to high intensity LED lighting for your tank.
  • It’s important to place them in a spot with adequate lighting and proper water flow.
  • If there are algae growing over them, they should be removed as soon as possible with a soft bristle toothbrush. Otherwise, there will be fish and gritters disturbing them all the time.
  • Not trimming the polyps in time can cause them to grow in unwanted places, even over other corals.
  • Green star polyps will take a while to acclimate and open up in a new environment.

Now that you know all the important information about green star polyps, you should have no trouble growing them out in your tank. Get ready to let their vibrant colors fill your tank with life!

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