If you’re looking for an ideal beginner coral there are few better species out there to try than Green Star Polyps, a personal favorite of mine. A mature colony has a grassy look to it that adds a fascinating new dimension to any aquarium.
Green Star Polyps are also fantastically versatile in aquascaping. They can be used to form a substrate carpet, grow on rocks like typical coral, and can even form living walls up the sides of your tank!
What are Green Star Polyps?
Green Star Polyps are a familiar face among the dizzying array of corals available in the reef hobby. Most reef aquarists have experience at some point or another keeping Green Star Polyps. They are beautiful, easy to care for, fast-growing, easy to propagate, and inexpensive; everything a first time coral keeper wants to hear!
Green Star Polyps are soft corals but they don’t simply exist as an exposed, fleshy mass. They grow a rubbery mat called a stolon that they can retract into when threatened. The stolon is likely an evolutionary bridge between true soft and true hard corals as it forms an encrusting layer over any surface it’s grown onto, much like the skeleton of true hard corals.
While they are fascinating, these corals do have some issues to keep in mind. Green Star Polyps are incredibly invasive to the point of being hard to get rid of in certain conditions. When they are happy with your tank they will grow, and grow, and grow…Often overwhelming other corals with their fervor.
But as long as you’re aware of their quirks, you’re in for a real treat. They also do very well alongside fish and are excellent soft corals for aquarists looking to dabble but don’t want to go all-in on coral equipment. They do like moderate intensity lighting but are tolerant of low light conditions and less than ideal water quality.
In short: Green Star Polyps are an excellent beginner’s coral so long as you’re up for some aquascaping!
- Common Names: Green Star Polyp, Daisy/Starburst/Mat/Eight Tentacle Polyp
- Scientific Name: Pachyclavularia sp.
- Origin: IndoPacific
- Size: Variable
- Aquarium Volume: Any
- Growth Rate: Fast
- Temperament: Aggressive
- Ease of Care: Easy
Green Star Polyp Care
While they are aggressively fast growers Green Star Polyps are straightforward to grow and propagate!
Water Conditions for Green Star Polyps
Green Star Polyps thrive in a wide range of water conditions, which is a major factor in their appeal. They thrive in most tropical temperatures (72-82℉) and standard marine chemistry (pH 8.0-8.24 and a salinity of 1.023-1.025).
Unlike some other corals they do prefer moderate to high water flow around them. In the wild they are found along reef flats and inshore reefs where currents are stronger. The continuous water flow helps them shed mucus and detritus as well as fully expanding the polyps.
Constant flow also provides a steady source of dissolved organic molecules for them to absorb and keeps macro algae from growing over them. They are very prone to algae and even Aiptasia anemones growing in between their polyps and strong current keeps problem organisms from taking hold.
While they aren’t hard corals Green Star Polyps still do need access to calcium to form the sclerites that give their bodies structure. Sclerites are little nodules of minerals that, combined with seawater, hold the coral upright.
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Magnesium is also required by corals as it helps make calcium bioavailable, as well as trace amounts of strontium. Fortunately, a reef aquarium supplement provides plenty when dosed after every water change.
Water Conditions for Green Star Polyps:
- Temperature: 72-82℉
- pH: 8.0-8.24
- Specific Gravity: 1.023-1.025
- Current: Moderate to High
- Alkalinity: 8-11 DKH
- Calcium: 400-450 ppm
- Magnesium: 1200-1350 ppm
- Nitrate: 1-10ppm
- Phosphorus: 0ppm
Lighting for Green Star Polyps
Green Star Polyps prefer low to moderate light intensity, not too low and not too high. They are tolerant of low light conditions of 35-50 PAR but you are very unlikely to see rapid growth. They may even stall out on you because Green Star Polyps are heavily dependent on their algae symbiotes for food.
Therefore, moderate lighting intensity (50-150 PAR) is best for these corals to ensure they grow continually. A mixture of actinic (10,000K) and full-spectrum (6700K) lighting will both fuel photosynthesis and bring out the fluorescent tones in your corals.
If they get too much light the polyps will close up and may even bleach. That said, they will grow just about anywhere in the tank and can be placed in all levels of the water column.
Aggression in Green Star Polyps
Green Star Polyps are one of the more aggressive coral species out there. They don’t rely on chemical warfare as Toadstool Corals do nor do they release far-reaching sweeper tentacles at night like Torch Corals.
Instead, the warfare strategy Green Star Polyps use is “expand and overwhelm” the adversary. They grow incredibly quickly; up to an inch per month if the conditions are just right for them. This makes aquascaping with Green Star Polyps exciting but also a challenge.
Once placed you can use Green Star Polyps to completely coat your substrate in a waving green grass-like carpet. The coral will even grow straight up the sides of aquarium glass, giving you a living background that prevents coralline algae and other unsightly organisms from colonizing it!
However they will also grow right over slow growing or more peaceful coral species like Pagoda Cup Coral (Turbinaria peltata). Even noxious corals like Leather Corals may have Green Star Polyps attempting to crawl up their base despite their toxic mucus.
Therefore you’ll need to be proactive at trimming Green Star Polyps back. If you have them growing on a sand or gravel substrate you should be especially careful about when and how they attach to live rock.
Once they start growing in among the rock pores, getting them off will be nearly impossible. Any leftover fragments of the colony you miss will likely regenerate into a brand new coral, making them a more invasive species.
Another strategy is to intentionally keep them with aggressive coral species. Corals with long sweeper tentacles will have an easier time keeping the Green Star Polyps at bay with their stings.
Lastly, it’s worth mentioning that Green Star Polyps are somewhat taxonomically confused so many related species are often sold under the other common names listed earlier. Many of these other Pachyclavularia sp. can be vivid purple, orange, or a more subdued brown (Brown Star Polyps).
Brown Star Polyps in particular are not only aggressive growers but suspected of also engaging in chemical warfare. These corals can release cocktails of terpene chemicals that slow or halt the growth of nearby corals.
This allows the fast-growing Brown Star Polyp to more easily overwhelm it’s rival for light and living space! Green Star Polyps aren’t believed to engage in this sort of behavior.
But if you see a drastic decline in coral growth rates as your Green Star colony expands it’s likely they are at fault. Coral terpenes can be easily dealt with by using activated carbon in your filter and performing more frequent or heavier water changes.
Tank Mates for Green Star Polyps
Green Star Polyps don’t sting or release poisons into the water column. They are also beautiful and easy to care for. You’d think they’d be model reef inhabitants but their desire for living space is boundless and a threat to peaceful, slow-growing species.
Aggressive corals are therefore an excellent match for Green Star Polyps because they are better at keeping the space around them free from intrusion. Some of these include the Galaxea Coral (Galaxea fascicularis), Torch/Frogspawn/Hammer Corals (Euphyllia sp.), and Acan Lords (Micromussa lordhowensis).
Acan Lords can also spit out mesenterial filaments to literally digest nosy neighbors. An excellent defense against a pushy Green Star Polyp colony that wants to move in. Another good choice are corals with toxic slime like Toadstool Corals (Sarcophyton sp.)
Be careful when keeping Green Star Polyps alongside other sessile invertebrates for this reason. Anemones can ward off the colony with stinging tentacles but serpulid (hard tubed) Feather Duster worms, clams, sponges, and other immobile creatures can be grown over faster than you think.
Since they grow so aggressively Green Star Polyps are excellent soft corals to keep alongside fish that are quasi-reef safe, such as Pygmy Angelfish (Centropyge sp.) and larger Damselfish. These fish don’t make a habit out of eating coral but they may bite at them occasionally, which can stress more sensitive, slower growing species. Green Star Polyps will hardly notice.
And of course, fully reef-safe fish are an excellent match, including many Clownfish, Mandarin Gobies, Basslets, Cardinalfish, Blennies, Firefish, etc. Green Star Polyps will also thrive alongside Shrimp, Snails, most Starfish, and other invertebrates.
Animals of any kind are ideal tank mates for Green Star Polyps because they provide a constant source of dissolved organic matter through their waste and leftover food.
Good Tank Mates for Green Star Polyps:
- Aggressive Corals (Galaxea, Euphyllia, Sarcophyton, Micromussa sp.)
- Noxious Corals (Leather, Toadstool Corals)
- Reef safe and non-coral eating fish in general
- Most marine invertebrates
Poor Tank Mates for Green Star Polyps:
- Coral-eating Animals (Butterflyfish, Peppermint Shrimp, etc)
Feeding Green Star Polyps
Despite their ridiculous growth rate Green Star Polyps are almost entirely photosynthetic! Most corals that grow this fast need extra food to sustain their bulk. Green Stars do take in dissolved organic nutrients as well as phytoplankton in the wild. But larger pieces of food, such as brine shrimp, mysis shrimp, or coral pellets are wasted on them.
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If you want, you certainly can offer them a dissolved organic molecular blend or plankton solution to fuel their (as well as your other corals’) growth rate. The Green Star Polyp should visibly react, extending its polyps to collect the food. But it’s not really necessary for them.
Good lighting and a trickle of dissolved compounds is all they need to thrive. Instead, you should focus on current, lighting, and ensuring their tank mates get food, which the Green Star will consume second-hand!
Propagating Green Star Polyps
Green Star Polyps are one of the easiest corals to propagate. If you’ve never propagated a coral (fragging) before these are a great place to hone your technique.
Fragging a coral involves splitting it into pieces. Corals, unlike higher animals, can regenerate themselves almost without limit, forming clones of the parent that grow into new colonies. Most corals also reproduce sexually and have distinct genders. However sexual spawning requires signals from lunar light and the seasonal tides that corals don’t receive in aquariums.
Unlike many other soft and hard corals Green Star Polyps don’t generally drop pieces of themselves behind to waft away into the current. They simply grow outwards, expanding their flat, rubbery stolons and adding fleshy polyps into it as they go.
The best way to propagate them is to simply snip off pieces of the leading edge that you don’t want to expand any further. If your Green Star Polyp colony is encroaching on the space of a more peaceful coral, you can take the fragments you’ve cut, soak them in a solution of aquarium water and iodine for 5 minutes, and then glue them to frag disks or coral rubble.
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You can also cut more deeply into the stolon to frag the colony into as many pieces as you wish. Try to shake the colony up a bit to encourage it to retract its polyps first as this will limit the amount of flesh damaged by your cutting. Sharp, sanitized coral fragging tools are essential here to prevent jagged tears in flesh that are ripe for infection as well as an iodine soak post-cutting.
You can also place a rock or other hard surface in the path of their growth, knowing that the Green Star Polyps will eventually grow over it. Once this happens, you can lift up the rock and cut away the newer colony and have an instant frag to place wherever you wish!