Metallic Green Star Polyp Coral (GSP)

Quick facts

Identity

Also known as

GSP; Star Polyps; Green Star Polyp Mat; Metallic Green Star Polyps

Synonyms

Clavularia violacea; Briareum violaceum

Environment

Saltwater

Native to

Fiji, Tonga, Solomon Islands, Indo-Pacific, Great Barrier Reef

Habitat

Shallow reef flats and lagoons where it encrusts rock, rubble, and other hard substrates in well-lit, current-swept water

Sourcing

Aquacultured

Conservation

Not Evaluated

Care

Care level

Easy

Coral type

Soft

Temperament

Semi-Aggressive

Growth form

Encrusting

Adult size

from 1 in (2.5 cm)

Spread

24 in (61 cm)

Growth rate

Fast

Placement

Low, Middle

Water

Temperature

76 – 80 °F (24 – 27 °C)

pH

8.1 – 8.4

dKH

8 – 10 dKH

Salinity

1.024 – 1.026 SG

PAR

50 – 150 PAR

Flow

Moderate

Light

Medium

Reef care

Nutrient preference

Medium

Alk/Ca uptake

Low

Target feeding

Beneficial

Give it room

4 in (10 cm)

Colors

Green, Purple

Feeding & breeding

Diet

Photosynthetic

Foods

Frozen, Phytoplankton, Zooplankton, Coral food

Propagation

Fragging

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Care guide

Overview

Wild colonies of this species encrust shallow, current-swept reef flats across the Indo-Pacific, and aquacultured frags now dominate the hobby trade. A purple mat carries dense metallic-green polyps that give a grass-like carpet effect over rock or glass. Fast-spreading and easy, it needs isolation from slower corals and periodic trimming to prevent overgrowth.

Care

Green star polyps encrust rock, glass, and overflow boxes with a thin purple mat topped by extending green polyps. It adapts to a wide range of light and flow but does best under moderate lighting and moderate, varied current that keeps the mat free of detritus and film algae. Stability of parameters matters more than any particular value, since sudden swings in salinity or alkalinity can cause the mat to recede or sulk.

Placement & acclimation

Frags are typically attached to a small rock or plug with coral-safe cyanoacrylate gel and set on an isolated island of rock or the aquarium's back wall to contain spread. Light-acclimate new colonies gradually over a week using shade or a reduced photoperiod to prevent bleaching, and dip before introduction to screen for pests. Position with good flow around the base to prevent detritus from settling on the mat.

Feeding

Most of its nutrition comes from zooxanthellae, so no direct feeding is required in a well-lit tank. Occasional dosing of phytoplankton or fine particulate coral foods during a lull in flow can boost polyp extension and coloration. Overfeeding is unnecessary and can contribute to nuisance nutrient levels without much visible benefit.

Neighbors

Because it spreads quickly over any hard surface, it is best kept on an isolated rock or frag plug set apart from the main aquascape, with several inches of clearance from slower-growing neighbors. It does not carry strong sweeper tentacles but can smother or outcompete corals it grows over given enough time. Fast stinging corals such as torches or hammers can damage the polyp mat if placed too close, so give both sides room.

Fragging

GSP is one of the easiest corals to frag: a sharp blade or scissors can cut a section of the mat along with its rock backing, which is then glued to a new plug or rock. Cut pieces reattach and resume growth within days to weeks under stable conditions, making it a common aquacultured starter coral.

Pests & problems

Closed or retracted polyps for an extended period usually point to low or stagnant flow, algae film smothering the mat, or a recent parameter shift rather than disease. Bleaching or pale patches can result from excessive light without proper acclimation, while patchy die-off along the mat's edge is often tied to shading or detritus buildup. Pest hitchhikers such as sundial snails or nudibranchs occasionally target GSP mats and should be checked for during a pre-dip inspection.

Sources

1. Green Star Polyps Coral Care Guide | Top Shelf Aquatics
2. Metallic Green Center Star Polyps Coral Care Guide | Top Shelf Aquatics
3. Green Star Polyps Coral Care - Frag Box Corals
4. Metallic Green Star Polyp Coral (GSP) - Pachyclavularia violacea – Reefamorous