Knotted Fan Coral, Melithaea ochracea

Knotted Fan Coral, (Melithaea ochracea), is a species of colonial soft coral that is found in tree-like fans on shallow reefs in the South China Sea between Taiwan and Indonesia, including Singapore and Malaysia. In Taiwan, it is the most widespread coral in its family Gorgonacea. It is found on the higher parts of reef fronts where its numerous small polyps can feed at water flow rates varying from 1.6 to 16 inches per second.

This species usually grow to about 8 inches in length, with some larger specimens recorded. It grows in one plane and has a branching, fan-shaped structure. The skeleton and branches are jointed, with swellings at the larger joints. The internodes are composed of hard, calcareous material while the joints are flexible and made of a horny material. The skeleton is covered by a flexible membrane, which contains tiny calcareous spicules (spike-like protrusions). The identity of these spicules is important for distinguishing between different closely related species.

In the Knotted Fan Coral, the branches of the coral are densely covered in calyces, dome-shaped perforated structures from which the polyps protrude. Colonies vary in coloration but tend to be shades of yellow, orange, red and white, sometimes with contrasting colors for the calyces and polyps. This coral is unique in that it does not contain symbiotic algae like most other forms of coral.

Colonies of this species grow larger at depths under 10 feet deep, mostly seen in those around Singapore. In deeper water, down to 49 feet, colonies are much smaller and have more variant color combinations.

This is a common coral used in the reef aquarium trade. It requires a moderate flow of water to allow the polyps to feed on non-evasive zooplankton and probably also phytoplankton.

This coral is also popularly used in the jewelry industry under the name Red Spongy Coral. It is known as a spongy coral because of the porous nature of its structure. Bright orange-red specimens are the most desirable. While it is easy to work with, it is also easy to damage because of its delicate structure.

Knotted Fan Coral is sometimes farmed due to the fact that it grows more quickly than other corals used in the jewelry industry. Its harvesting is believed to be sustainable.