TankBud

Galaxy coral

Galaxea

Also known as Star Coral, Tooth Coral, Crystal Coral, Octopus Coral

SaltwaterCoral

Galaxy coral (Galaxea)
Diego Delso · CC BY-SA 4.0

Care at a glance

Temperature
75–81°F
24–27°C
pH
8.1–8.4
Adult size
11.8 in
30 cm
Minimum tank
20 gal
75 L
Temperament
Aggressive
Social behavior
Solitary
Swim level
Bottom
Difficulty
Medium
Breeding
Hard
Rarity
Common
Reef safe
Reef safe
Family
Euphylliidae
Origin
Indo-Pacific and the Red Sea, from East Africa and the Gulf of Aden to the Great Barrier Reef, Fiji, and Samoa

Overview

The galaxy coral is an aggressive, colonial large polyp stony coral that needs open space around it in a reef tank. It is a coral for a keeper past the beginner stage.

Did you know

The galaxy coral's sweeper tentacles can stretch to many times their resting length. Their reach is among the longest of any sweeper in the hobby, far beyond what a hammer or torch coral can manage.

Caring for the galaxy coral

Give a galaxy coral moderate light, around 75 to 150 PAR. Run medium to fairly strong, turbulent flow, but avoid a direct jet, which can cause tissue recession.

It needs a tank of at least 20 gal (75 L). Keep the water at 75 to 81°F (24 to 27°C) with a pH of 8.1 to 8.4. It feeds well on brine or mysis shrimp, and it also draws real energy from light.

Its sweepers come out both day and night, and at night they stretch to roughly 6 to 12 inches (15 to 30 cm). They sting anything within reach and can kill less aggressive neighbors.

Placement matters more than anything else, so give a galaxy coral its own island rock rather than a spot in the main aquascape. Leave at least 6 to 12 inches of open water on every side, well clear of anything its fully extended sweepers could reach. Treat that spacing as non-negotiable.

Propagating a galaxy coral calls for a saw rather than simple hand-snapping. The fused skeleton between its polyps is tougher to cut cleanly than a typical Euphyllia branch.

Good to know

Galaxea belongs to the family Euphylliidae and is related to Euphyllia, despite its very different star-studded look. Each polyp sits in its own star-shaped corallite tipped with tiny contrasting points. Those corallites give it both the galaxy coral and star coral names. Its skeleton is notably brittle and fractures easily, which is where another common name, brittle coral, comes from.

In the wild

Galaxea ranges across the Indo-Pacific and Red Sea, from East Africa and the Gulf of Aden to the Great Barrier Reef, Fiji and Samoa. It forms encrusting to mounding colonies on reef slopes with weak wave action, typically in shallow water only a few meters deep. Wild colonies can eventually grow into columns several meters across.

Common questions

What size tank does a galaxy coral need?

A galaxy coral needs at least 20 gal (75 L).

What temperature and pH does a galaxy coral need?

A galaxy coral is comfortable at 75–81°F (24–27°C) with a pH of 8.1–8.4.

What does a galaxy coral eat?

A galaxy coral feeds well on brine or mysis shrimp. It also draws real energy from light.

How big does a galaxy coral get?

An adult galaxy coral reaches about 11.8 in (30 cm).

Related species