Marine Aquarium, The Pulse Coral

The successful marine reef aquarium is a wonderful sight, not just to the aquarist but to anyone. It shows Mother Nature’s creations supported by human invention, but basically it’s just beautiful. Achieving a successful captive mini-reef requires the usual – patience and research, the latter is easy. The two major requirements are first, above all else, high seawater quality and second but close correct lighting for the corals which benefits the zooxanthellae within the corals. Basic research answers the questions the two requirements raise, its quite straightforward.

The pulse coral, Anthelia glauca, is reasonably easy to keep. There is another coral that is similar, Xenia elongata. They come from Indo-Pacific reefs. The pulse coral is more bush like, Xenia elongata is more like a tree shape with a body from which branches grow, whereas the pulse coral Anthelia glauca has an encrusting mat from which the polyps grow. These polyps are cylindrical and long, the length can be up to around 5 inches (circa 13cm). The colour can vary from coral to coral, being cream, brown, ivory or grey. The reason they are called ‘pulsing’ is that the polyps could rhythmically open and close somewhat like a human hand, this action is not guaranteed. If pulsing does not occur this is not a definite indication that the coral is not healthy.

When purchasing either type of pulse coral it is best to obtain one that is firmly attached to a piece of rock. This way it is easier to place in the aquarium even though room has to be made for the rock. Transportation will be in the original seawater of course but on arrival at the destination aquarium action is required to ‘equalise’ the seawater. There are two main ways of doing this, the first requires more attention. Take half or so of the seawater from the bag and replace it slowly, a small spoonful at a time until the level has returned to the original. Then remove half again and do the same. The coral should not be exposed to the air at all. Once this has been done the bag can be placed in the aquarium and left for a while, say 30 minutes, to allow the temperature to adjust. When this has been done the coral and rock can be removed and placed in position. The position can be selected when waiting for the previous actions to be completed. The second and better way is called the ‘drip method’. This simply means that a thin plastic tube is used and a dripping flow is started. This is directed into the bag after half or so of the original seawater has been removed. This method will be more successful in slowly placing aquarium seawater in the bag. When the seawater has reached the original level take half out and resume the drip. Then place the bag in the aquarium and allow the temperature to adjust. The coral can then be removed and placed in position, always ensuring it is underwater and not exposed to air.

Anthelia glauca tends to slowly spread on its base from rock to rock, this doesn’t cause problems. Sometimes the coral doesn’t pulse as expected but this is not an indicator of health problems. The coral is still attractive and a good addition. The coral is not as strong a competitor for space as some other varieties and could on occasion require a little assistance. As with all corals ensure that the coral is not being detrimentally interfered with by others close by. The coral appreciates a reasonable flow of seawater but not a powerful one, so ensure pump outlets are positioned properly.

It is thought that the pumping action that could be observed is because of the pulse corals partial dependence on dissolved organic matter*. However dependence on organic matter is very much secondary to the main dependence on zooxanthellae* so problems should not develop if there isn’t any pumping action. It has been suggested in earlier times that the pumping action is for oxygen but, from the reference given, this appears not to be the case. I am not aware of any science references.

If seawater quality is maintained to a high standard and the lighting is maintained with renewal of the source, (that is bulbs, Led bulbs, fluorescent tubes etc), as required then the Pulse Coral should prosper and hopefully spread. It is a very attractive coral and a worthy addition to the reef system.

(*Aquarium Corals. Eric H. Borneman)