Propagating Tubastraea diaphana (Diaphana Sun Coral)

Propagating the sun coral Tubastraea diaphana: a non-photosynthetic species grown by colony budding and dependent on regular zooplankton target feeding.

Overview

Tubastraea diaphana is one of the sun corals in the genus Tubastraea, large-polyp stony corals with hard, non-reef-building skeletons whose polyp colours span yellow and orange shades. Like all members of the genus it is azooxanthellate, lacking symbiotic zooxanthellae and extending long tentacles at night to catch passing zooplankton, with large polyps that can take relatively large prey.

Reproductive Mode

Tubastraea species reproduce both sexually, by releasing planula larvae, and asexually. The genus spreads by budding and by forming runners that can extend over 10 cm per year, generating new polyps next to the parent colony.

Fragging / Asexual Propagation

Propagation uses this asexual budding. As the colony grows and adds polyps, daughter polyps or colony sections are separated and remounted onto rubble or plugs; larvae that settle nearby in the wild typically do so within about a metre of the parent and can likewise be grown on.

• Let the colony bud and add polyps.
• Detach daughter polyps or a section of colony.
• Mount each piece onto rubble or a plug.
• Target-feed every piece until established.

Feeding & Conditions for Propagation

Sun corals accept foods such as frozen mysis shrimp. Feeding every other day is sufficient for survival, while daily feeding enables faster growth, which speeds the build-up of new frags. Each polyp is target-fed because the coral draws nothing from light.

Sexual Reproduction

Sexual reproduction in Tubastraea produces planula larvae that can survive up to about two weeks; it has been recorded in spring, summer and winter. As with its relatives, aquarium propagation relies on asexual division rather than larval rearing.

Common Challenges

Starvation is the central risk: a sun coral that is not target-fed consistently will decline. Sun corals are regarded as relatively easy among non-photosynthetic corals, but only where the feeding routine is kept up and the resulting nutrients are exported.