The Pulse Corals Xenia sp. are some of the most endearing corals, and are highly favored by reef enthusiasts. With their pulsing heads and the gentle waving of their polyps in the water, they produce an almost mesmerizing affect to the viewer. Since they tend to grow in the direction of the water flow that they are near, you can get them to grow where you want in the reef tank. Getting them to grow up the back wall of the aquarium makes for an interesting display.
Most species from the Xenia genus have unbranched stalks that are short, thick and smooth, from which the polyps arise. They can be cream, white brown, ivory and light green. The color is uniform with just a little contrast between the stalks and polyps. The polyps can contract considerably but do not retract inside the coral. Not all Xenia pulsate, but the species that do will generally pulse about 8 times per minute, yet there can be quite a variation in the strength and speed of the pulsing action.
There is no proven reason why Xenia corals pulse. Many experts and aquarists attribute a variety of reasons for the pulsing phenomena. One thought is that they are pulsating to help with respiration and gas exchange. Water chemistry also plays a role in their pulsing, along with lighting and current, just what combination is hard to tell. They are sensitive to falling or low pH and will stop pulsing when the pH is below 8.3. Adding small amounts of carbon will take some organics out of the water. Some aquarists have found this to induce the polyps to pulse, as if the coral is trying to try pull more nutrients from the water. Supplements of iodine are also suggested by some, but with caution as Lugol's has been found to be detrimental to some Xenia colonies. If your Pulse Coral is pulsing, then keep doing what your doing!
The Xenia corals are not the only pulsing corals. The Xeniidae family itself is considered unique in the coral world because of this ability. From this family, at least five other genera will pulse. Some of those common to aquarists include the Pom Pom Zenias of the Heteroxenia genus and the Waving Hand Coral or Glove Coral Anthelia sp.. Anthelia corals form an encrusting mat and their cylindrical polyps grow directly from that base. Xenia are different from Anthelia since Xenia polyps rise from a capitulum (top of the stalk) forming small colonies that are only a few inches tall (up to 4").
The Pulse Coral Xenia sp. can be easy to care for, depending on proper handling procedures. If you need to handle them, do so very briefly and with gloved fingers. When handled they stress and produce lots of mucous, which in turn attracts bacteria, leading to death. This is also the reason they do not travel well. This production of mucous attracts bacteria, and being trapped in the shipping bag causes the bacteria to consume the Xenia. Though their primary difficulty is in shipping, once established in the aquarium they can be very hardy and are one of the fastest corals to multiply.