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Green Star Polyps

Green star polyps (GSP) are the classic starter coral - a purple mat that erupts in a lawn of bright green, star-shaped polyps and grows over almost anything.

Last reviewed: October 2026

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Overview

Green star polyps (GSP) are the classic starter coral - a purple mat that erupts in a lawn of bright green, star-shaped polyps and grows over almost anything. They are an animal, not a plant, and they are so vigorous they are best kept on their own island of rock. (Pachyclavularia violacea.)

Origin & Habitat

Indo-Pacific reefs, growing as encrusting mats over rock and rubble in bright, moving water.

Appearance

A rubbery purple base membrane studded with fuzzy green polyps that open into eight-armed stars; closes to a flat mat when disturbed.

Placement & Temperament

Peaceful to its neighbours but aggressively fast-spreading - it will encrust over other corals' bases. Keep it on an isolated rock or ledge with a moat of bare sand around it.

Tank & Water Conditions

Salinity 1.024-1.026, 24-27°C (75-81°F), stable alkalinity 8-11 dKH, calcium 400-450 ppm, magnesium 1300-1350 ppm. A cycled, stable tank.

Lighting & Flow

Low to moderate light (roughly 50-120 PAR) and moderate flow; tolerant of a wide range.

Feeding

Mostly powered by its symbiotic zooxanthellae (algae in its tissue) via light; little or no target feeding needed.

Health & Growth

Extremely hardy - one of the first corals most reefers keep. A sulking mat that stays closed for days usually signals water instability or being freshly moved.

Pros & Cons

Pros

  • Bright, fast, forgiving beginner coral
  • Thrives across a wide light range
  • Cheap and endlessly fragged

Cons

  • Weedy: encrusts and overtakes rock
  • Hard to fully remove once established
  • Best isolated from other corals

Everyday gear for a reef tank

Reef salt mix Mixed fresh for every reef water change. Check price Refractometer Reads salinity, a number worth checking often. Check price Reef light Matched to the light level the care section gives. Check price Reef test kit You cannot manage what you cannot measure. Check price

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Green Star Polyps - frequently asked questions

Is green star polyps good for beginners?

Yes - it is one of the hardiest corals in the hobby. The only catch is its speed: keep it on its own rock so it cannot overgrow slower corals.

Why won't my GSP open?

Usually recent handling, a swing in water parameters, or too little flow to keep it clean. Give it stable water and a few days.

More corals to explore

Hammer Coral Hydnophora Coral Kenya Tree Coral Leptastrea Coral Lobophyllia Coral Montipora Montipora Digitata Mushroom Coral Pavona Coral Plate Coral Pocillopora Coral Porites Coral
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