second photo by Bob Fenner,
last photo by Robert Pacheco
Common names: moon coral, acan
Natural origin: Indo-Pacific
Sensitivity (Level 2): Care difficulty for these corals depends on species, but most are generally tolerant and forgiving when healthy.
Feeding: These corals have strong prey capture ability. In addition to feeding tentacles, these corals are also known to extend their stomachs, mesenterial filament bundles which dissolve and digest their neighbors. They should be fed at night since this is when they usually extend their feeder tentacles and/or mesenterial filaments. If after several weeks your coral is still not extending feeder tentacles, you can try to encourage a feeding response with night-time target feeding. When doing this, wait one hour after lights go off before feeding. Turn water flow off so that the food can fall and rest onto the coral. Give the coral an hour or two to "grab hold" of the food, then turn water flow back on. Do this regularly until feeder tentacles extend regularly in anticipation of feeding. Once your coral is readily extending feeding tentacles, it will be able to catch food from the current without any assistance.
Lighting (Level 3 to 6): These corals can adapt to a wide range of light intensities. Start by placing the coral lower down in the tank and move up if necessary. As with any coral, bleaching can occur if not properly acclimated to a sudden change in lighting.
Waterflow: Moderate water flow is recommended.
Placement: These are very aggressive corals. Their mesenterial filaments can and will dissolve the tissues of other corals within reach, so please give them plenty of space to avoid contact with other corals.
General: Like many corals, they can take some time to "settle in" to a new home. Wait a few weeks to see normal feeding behavior before worrying.
These corals are often confused for corals of the Faviidae family or for their Blastomussa and Micromussa cousins. Acanthastrea have exceptionally large, pointy septa (skeletal "teeth") that help distinguish them from other corals. However, you may never know exactly which kind coral you have without close examination of the coral skeleton.