Pulsing Xenia

Pulsing Xenia is a soft coral recognized by its "pulsing" movement, opening and closing its polyps several times a minute. The colony consists of soft stalks rising from a base, with polyps clustered like a bouquet at the tip of each stalk; each polyp has eight feathery tentacles. Its color can be white, cream, light brown, pink or bluish. The reason for the movement has not been fully explained; it is thought that by stirring the water around the polyps it makes gas exchange and photosynthesis easier.

In the trade, names such as "pulsing xenia" and "pom pom xenia" are used loosely for different Xenia and Heteroxenia species; Xenia elongata is also among the commonly sold species, and its care is the same. Because it spreads so much in the aquarium, it requires control. Unomia stolonifera, from the same family, has been reported to be invasive on the coasts of Venezuela, most likely having arrived there through the aquarium trade: never dump Xenia pieces or water containing these corals into the sea or the wild.

It forms large colonies on shallow reefs of the Red Sea and the Indian Ocean, on well-lit rock surfaces and on dead coral.

• Light: Moderate light (roughly 100–200 PAR). If the light is too low, the stalks stretch and the pulsing slows down.
• Flow: Low to moderate, indirect flow. In strong flow the polyps may stop pulsing.
• Placement: The middle part of the rockwork, if possible on a stone separate from the main structure.
• Water parameters: Salinity 1.024–1.026; KH 7–11 dKH. It likes water with some nitrate and phosphate; it declines in overly stripped aquariums.

Xenia have weak digestive structures and hardly take particulate food. They get their nutrition from zooxanthellae and from dissolved substances they absorb directly from the water. No target feeding is needed.

It has no stinging tentacles and its chemical defense is weak; the harm to its neighbors comes from its rapid spreading. It extends new stalks sideways, settles into the pores of the rock and can spread over slow-growing corals. Do not keep it on the same rock as SPS and LPS; grow it on a separate stone with at least 15 cm of space around it.

It is compatible with fish and the cleanup crew. Some dwarf angelfish and butterflyfish eat the polyps.

It spreads on its own by putting out new stalks. A stalk is cut at its base and tied to a small stone with a rubber band, or placed on top of the stone and kept under a mesh or a perforated cup for a few days; glue does not hold. It attaches to the new surface within about a week.

• Sudden crash: Sometimes a colony that has been doing well melts away within days. The exact cause is unknown; sudden changes in salinity or KH, overly stripped water and high temperature are the most suspected factors.
• Not pulsing: Strong flow and low light are the most common causes; a healthy colony also slows its pulsing from time to time.
• Uncontrolled spreading: Regularly cut the spreading stalks and remove them from the aquarium.