Black Sun Coral

Tubastraea micranthus, known as the Black Sun Coral, forms dense, bushy colonies often exceeding 1 meter (3.3 ft) in diameter. Its robust polyps, dark green to black, extend fully and can reach 1 to 2 cm (0.4-0.8 in) in diameter. Each polyp has numerous tentacles arranged radially, giving them a flower-like appearance. The genus name Tubastraea refers to the tubular shape of its corallites. Its common name "Sun Coral" refers to the radial arrangement of tentacles which can resemble a sunburst, though T. micranthus lacks the typical yellow and orange colours of its relatives.

This azooxanthellate coral lacks symbiotic algae and therefore inhabits shaded, low-light environments. It commonly attaches to reef overhangs, inside caves, and in deep crevices, typically at depths of 5 to 40 meters (16-130 ft). As a heterotrophic feeder, it captures plankton and other small particles from the water column with its extended polyps, which are usually open during the day and night. Its presence provides habitat and shelter for various small marine creatures, including fish and invertebrates. However, when established in dense colonies, it can be competitive and sometimes overshadow other coral species.

Reproduction occurs both sexually, through the release of gametes into the water column, and asexually, via budding. Asexual budding allows new polyps to form directly from the parent, contributing to the growth of large, contiguous colonies.