Propagating Tubastraea micranthus (Black Sun Coral)

Propagating the tree-like black sun coral Tubastraea micranthus: an azooxanthellate species that grows from colony division and demands night feeding on plankton.

Overview

Tubastraea micranthus, the black sun coral, grows and branches into bush- or tree-like colonies and is characteristically dark, often dark green. Its polyps expand up to 3 cm at night to capture prey. Colonies can be large: Philippine specimens reach 1 m tall with 15 cm bases, while Red Sea colonies top out around 44 cm. It is native from the Red Sea to Madagascar and into the Pacific to Fiji.

Reproductive Mode

Being azooxanthellate, the coral relies entirely on capturing planktonic organisms at night and grows at roughly 4 cm per year. It is presumed to reproduce both sexually and asexually, based on its similarity to related Tubastraea species.

Fragging / Asexual Propagation

As with other Tubastraea, propagation works through asexual division of the branching colony. Sections or daughter polyps from the tree-like growth are separated and remounted, with each new piece needing its own feeding to establish.

• Let the tree-like colony branch and add polyps.
• Separate a branch section or daughter polyps.
• Mount each piece onto rubble or a plug.
• Provide good flow and night feeding for each frag.

Feeding & Conditions for Propagation

Its primary diet is planktonic organisms captured at night, and it has been observed taking larger prey such as jellyfish. Unusually for an azooxanthellate coral it is reef-building and remains standing in high-energy environments, so frags benefit from strong flow alongside heavy feeding.

Common Challenges

Slow growth (about 4 cm per year) and a strict feeding requirement make this one of the harder Tubastraea to build up from frags. The heavy feeding needed also loads the system with nutrients that must be exported, and any escaped material poses an invasive risk.