How to Care for Green Star Polyps

Green Star Polyps (Pachyclavularia sp.)

Green Star Polyps (Pachyclavularia sp.) are a type of soft coral that is a fan-favorite for both beginner and advanced aquarium hobbyists.

Green Star Polyps are easy to raise, spread easily, and can be found both online or in pet shops. Love them or hate them, it is not possible to deny that they can also be extremely fluorescent and attractive in a reef aquarium where they look like hills of grass swaying in the wind.

Keep reading for more information about this amazing polyp, including how you can care for Green Star Polyps in your aquarium, the PROS and CONS, and if these are the right corals for you at all. 

Quick Notes about Green Star Polyps

Name Green Star Polyps
Other Names
GSP, Daisy Polyps, Star Polyps, Brown Star Polyps
Mat Polyps, Starburst Polyps, Eight Tentacle Polyps
Scientific Name Pachyclavularia sp.
Tank size (minimum) 5 gallons (~20 liters)
Keeping Easy 
Propagation Easy
Moderate to high
Water flow Moderate to high
Optimal Temperature 22 – 28°C  (~72°F – 83°F)
Optimal Salinity SG = 1.023 – 1.025
Optimal PH 8.1 – 8.4
Optimal KH 8 – 10
Nitrate Less than 10 ppm
Feeding Does not require
Growth Form
Growth Rate Fast
Invasive Very
Aggressiveness Peaceful (Does not sting)
Color Form From light green to dark green

Natural Habitat of the Green Star Polyps

The Pachyclavularia Genus of Green Star Polyps are normally found in the Indo-Pacific oceans. The polyps dwell in reefs and lagoons around rubble, usually near Xenia and clavularia. The waters they are found in usually have low water flow and are high in nutrients. 

Description of the Green Star Polyps

Green Star Polyps (Pachyclavularia sp.)Green Star Polyps have a purple or red mat and eight green, yellow, or light green tentacles, that look very pretty especially under some blue lights. The tentacles are smooth, thin, and surround a center opening called a mouth. The mouths tend to be in a different color.

Depending on the species, there are different variations of color on how much green (from light green to a really deep green) they have or how much purple they have on them.

They can reach a height of 2 – 4 cm (1 – 1.5 inches) in a month, colonies can grow and occupy a significant area on the surface of the reef.

Green Star Polyps can retract into the mat (also called a stolon) when they sense a disturbance. A disturbance can be caused by trimming or cutting the coral, and fragging. The polyps may also retract at night time or when they are feeling stressed. 

Feeding Green Star Polyps

These polyps are partially filter feeders. The Green Star Polyps live in a symbiotic relationship with zooxanthellae that live inside them which provide them with nutrients. The zooxanthellae need photosynthesis to produce nutrients so light is essential. Food can also be snagged that floats by. That is why people often mistakenly say that GSP do best in dirty water.

Please, do not confuse dirty water and nutrient rich environment. Dirty water is just a recipe for disaster in the long run. Although Green Star Polyps are pretty resilient and can tolerate a dirty tank, it will not end well anyway. Eventually, you will get some serious problems with the livestock or run into major algae issues.

However, when we are talking about nutrients, we usually mean all kinds of things like suspended food particles, elements the foods break down into, for example, amino acids as well as the end result with nitrates and phosphate.

In general, you don’t have to worry about feeding them in the reef set up. Green Star Polyps will perfectly well underneath the lights that you have in your tank. However, if you want them to grow even faster and you want them to have some better color on them I would definitely recommend feeding some liquid food to them. 

Keeping Green Star Polyps

The Pachyclavularia genus is extremely hardy and one of the easiest to keep and care for. It takes a lot to kill Green Star Polyps if you thank that you are going to mess them up. So, do not worry if you are a beginner and a little bit scared of what to get.

Tank Size

The tank size for Green Star Polyps does not matter at all. With time they can spread to the entire surface of the tank, regardless of its size. As long as you have stable water parameters it is possible to keep them even in small nano reef tanks like 5 gallons (20 liters).

Lighting Requirements

The Green Star Polyps require moderate to high light. If it is possible, go for higher intensity lighting conditions. More intense lighting often results in brighter more intense coloration.

Actinic blue lighting will bring out the color of your polyps but Green Star Polyps can survive with most types of light. You can also use traditional T5 fluorescent light.

Another light type that may be used are metal Halides, but metal Halides are usually too strong for the polyps and are not recommended. If the light you are using is too strong, you will notice your coral start to go pale and ‘bleach’ themselves.

Water Movement

Water movement is also crucial to your Green Star Polyps’ health. Actually, this is one of the main things you need to be absolutely sure. Your tank should have at least a moderate water movement. A good water flow will remove detritus and help your colony multiply and spread.

Optimal Water Parameters

For better growth it is recommended to have the following requirements:

  • Salinity of the tank should be in the 023 to 1.025 range.
  • Temperature should be between 72 and 83-degrees Fahrenheit (temperature equivalent in Celsius is 22 – 28 C)
  • Calcium is a great additive for your polyps. Calcium levels should be anywhere from 400 to 450 ppm
  • The alkalinity of the tank should range from 7 to 12 dKH with 8 – 10 being optimal.
  • Phosphate levels should be .10ppm or less. No Phosphates present is fine
  • Magnesium levels should be in the 1200 to 1350 ppm range
  • Strontium levels should range from 8 to 10
  • Nitrate levels should be 10ppm or below

If your nitrate levels are at 10 ppm, be sure to do a water change to lower your nitrate levels. If your phosphate levels are too high, you can change your phosphate media to lower your phosphate levels.

Water Changes

When it comes to water changes, you have the option of deciding what percentage of water should be changed and how often. You can do a 20% water change once a month if you prefer to perform water changes less often.

You can also do 10% water changes every 2 weeks. While either of those options are acceptable, it is recommended to do a 5% water change every week because water changes can add additives to the water that help your polyps. 

How to Limit the Spread of Green Star Polyps

Along with knowing how to keep your Green Star Polyps healthy, you should also know how to limit them. Green Star Polyps can grow out of control if you do not take steps to limit their growth. Actually, they are pretty invasive.

·        Isolation

Green Star Polyps (Pachyclavularia sp.)The best thing to do to limit polyp spread is to make sure that you plan your tank layout well. If you have a rock that you intend to grow polyps on, keep it away from other rocks. The polyps also tend to grow out and will most likely grow on whatever substrate you are using.

You can cut the coral off of your substrate which may be easier than removing it from rocks that it may have reached. If the polyps are growing up the side of your wall and that isn’t what you intended, you can also take a razor blade and scrape the coral off.

Note: Sand is your best hope. While GSP spreads on the sand it is very easy to frag back and keep under control. However, once GSP encrusts onto rockwork, it can be nearly impossible to remove. So if you don’t want these overgrowing other things in the area, it is best to keep them on an island so they only can grow onto the sand.

·        Restriction

You can put aggressive corals (like Frogspawn, Torch corals or something similar) along the perimeter of the Green Star Polyps. They will sting away the GSP and prevent any expansion.

Another cool trick to keep Green Stars polyps under control is using Aiptasia-X. By adding a line of it on the edges of the polyps, they will stop growing in that directions for some time. However, this is a temporary measure and you will have to repeat the process systematically.

·        Termination

Get a powerful laser and you can burn it in the spots you do not want it to grow. 

Toxic Additives to Green Star Polyps

Knowing what additives should be avoided is also crucial to your tank. Iodine and Aluminum Oxide (which can be found in certain phosphate removal sponges) should be avoided as additives because the additives can cause adverse effects. 

Fragging / Propagation

To frag your Green Star Polyps is to essentially propagate your polyps. You take the original mother colony and you remove a piece of the mat that is big enough to spread on its own. The original colony will spread to make up for the missing piece and you will then have a separate colony. There are a couple of ways to do this.

Things that you might need depending on your method:

Coral Fragging Kit tools. Profile - Vermetid snails. How to remove them


 Coral Propagation Fragging Kit Set  (link to Amazon)

Note: If you have an acrylic tank be very careful with sharp instruments. It is very easy to scratch acrylic. Whenever it is possible, use alternatives like an old credit card to scrape them off.

Warning: It is always a good idea to use latex gloves and protect your eyes when you are fragging any type of coral. Latex gloves will prevent any possible irritation of the skin and, of course, you don’t want the stuff in your eyes!

Method 1: Scrape and Peel

You can use a scalpel or knife to separate the edges of the mat from the rock that it is on. Be gentle and work slowly. The surface can be brittle and break off.

Once you have part of the mat lifted away, you can peel the rest of the mat that you are planning to use to spawn offspring. The hardest part is peeling because pieces can break off. It is okay to make mistakes because this kind of coral can be forgiving because of how it regenerates and how hardy it is.

Once your child mat is separated, attach it to a rock, another surface, or a plug pebble using cyanoacrylate glue. Just hold it there for a few seconds.

Tip: You can irritate them with your hand first so they will shrink. This way it will be easier to work with the polyps.

Note: Although moderate water flow is recommended but not for newly separated coral. Keep your water flow low in order to keep the piece from separating from the rock or surface. Moderate water flow is fine once the coral has attached itself firmly to the rock.

Also, people often ask, how long can they keep Green Star Polyps out of the water without harming them? These polyps are hardy, so, as long as they do not completely dry out, and as long as they do not get too hot or cold they should be OK. You can simply keep a bucket of tank nearby to dip them in if you have them out for a long time.

Method 2: Remove the rock

You can use a hammer and chisel to remove a chunk of the rock that the Green Star Polyp Mat is inhabiting. The rubble can then be separated and used to grow a new colony.

Method 3: Let nature do the work for you

You can use acrylic, regular rock, or a plug pebble and place it nearby the mother colony. Let the colony spread to the new surface. Then you can separate the one colony into two colonies. You can also use the acrylic for the scraping method. You can let the mother colony grow on the acrylic and use this smoother surface to scrape the smaller colony off easer.

With All Three Methods

There might be slime when you remove the offspring colony. That is normal and is nothing to be worried about. Running carbon may help the healing process for both mother and offspring colonies.

Normal water flow is fine for the mother colony. If a colony does not seem to be healing and seems to be infected, remove it immediately and place it in its own container to avoid further infection in the tank. 

Potential Problems of Green Star Polyps

Invasive: Green Star Polyps are an invasive species and in some tanks can even surely become a pest. This coral grows like a weed across any hard surface. Therefore, they should be kept at LEAST 6 inches (15 cm) away from other corals as the polyps could overrun the other corals.

Green Star Polyps attach themselves to just about any surface, whether the surface is a rock, a tube, glass, or even other coral. If a rock that they are occupying is getting full and there is nowhere left to expand, Green Star Polyps will send out purple growths to attach to another surface. A colony will then start to be created where the tendrils attach.

Green Star Polyps will need systematic maintenance to keep it sliced off the glass and trimmed away from the rocks. Under good conditions, Green Star Polyps can spread quickly in a tank but they can also overrun other corals that cannot fight back.

Do not open up: If you have noticed that Green Star Polyps are staying shrunk up and you can’t figure out why there are can be several reasons.

  1. Algae growth on the polyps can prevent them from receiving enough light and nutrition. For example, if you see an unusual activity of your clean up crew, constantly trying to get something off, it can be a sign of algae. If possible, take it out and clean it with a small paintbrush.
  2. You may not be giving it enough light or water flow for its needs. In most cases, the problem is water flow, they really need it.
  3. Another coral could be stinging it if you have other corals in your tank.
  4. There is a lot of debris on the corals. Remove it with a pump or turkey baster.

Green Star Polyps and Compatibility

Green Star Polyps do not have stinging tentacles so in theory, they would be very compatible with other species. But because of how invasive the species is, physical separation must be maintained to keep your Green Star Polyps from encrusting onto your other corals. These corals can easily take over a whole tank because of how they spread. 

Green Star Polyps and Tankmates

Green Star Polyps do well with well-fed fish, crabs, snails, or shrimp. They can also be homed with other corals if you are extremely careful and observant of growth progress. 

Buying Green Star Polyps

You can buy the Green Star Polyps in pet stores or online. The polyps will come attached to some sort of surface/rock so that it is ready to be inserted into a tank. Add your own rocks nearby to start a spread.

Tip: There is no need to buy a bigger section of it. Why pay more money when soon you will have more than enough? So, get a small one. They grow pretty quickly anyway. 

In Conclusion

Green Star Polyps are more than amazing for beginners. The polyps are very hardy and really low maintenance. You do not even have to worry about feeding them because they already come with what they need to feed themselves. The polyps also easily decorate a tank by their spreading and only require a little light to photosynthesize.

However, if you are looking to grow many different types of coral, this species may not be the best fit due to how invasive it is. But it is possible to keep the corals separate if you are really set on having Green Star Polyps with other kinds of coral.

Related articles:

Top 10 Corals for Beginners
How to Care for Bird’s Nest Corals
How to Care for Acan Corals
How to Care for Zoanthid Corals
Proper Care for Carpet Anemone
How to Care for Torch Corals
How to Care for Frogspawn Corals
How to Care for Hammer Corals
How to Care for Elegance Coral
How to Care for Duncan Corals
How to Care for Pulsing Xenia
How to Care for Ricordea Coral
How to Care for Palm Tree Polyp
How to Care for Kenya Tree Coral

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