Galaxea fascicularis Propagation Guide
Propagating galaxy coral Galaxea fascicularis: cutting between corallite clusters, healing frags, and isolating it from its very long, aggressive sweeper tentacles.
Overview
Galaxea fascicularis, the galaxy or star coral, is a large-polyp stony coral in the family Euphylliidae. Its skeleton bears circular, tube-shaped corallites less than 1 centimetre across, with ridge-like septa radiating from the centre. Colonies begin as low domes and become more irregular, massively hummocky or columnar with age.
Reproductive Mode
Galaxea fascicularis reproduces both sexually and asexually. Sexually, sperm and eggs are released into the water in synchronized spawnings for external fertilisation, and the resulting planula larvae drift before settling and undergoing metamorphosis. Asexual increase of the colony occurs by budding.
Fragging / Asexual Propagation
In the aquarium, this coral is propagated by cutting the skeleton between clusters of corallites so each fragment carries one or more intact, living corallites. A coral saw gives the cleanest division. As with other stony corals, retaining living polyp tissue on the frag is what allows it to regrow.
- Identify a section with several healthy corallites.
- Cut the skeleton between corallite clusters with a coral saw.
- Mount each frag so its living corallites face the light.
- Dip the frag to reduce infection risk while it heals.
Conditions for Propagation
Frags recover in stable reef conditions with medium light and flow. Galaxea also feeds heterotrophically on organic particles and zooplankton, so periodic feeding supports the energy demand of healing tissue.
Common Challenges
Galaxea is a notorious aggressor. Its sweeper tentacles can extend up to 30 centimetres (about 12 inches) and serve to deter other organisms from settling nearby. Even small frags must be given a wide isolation zone, because the sweepers reach well beyond the visible colony outline.