Genus Acanthastrea - Aussie Acans
Bold and Beautiful Corals from Down Under

Corals form the genus Acanthastrea remain very popular in the marine aquarium hobby, especially those coming from Australia. Their vibrant colors, ease-of-care and fascinating behavior are only a few of the reasons reef aquarists are drawn to these amazing animals. Frequently called “acans” by hobbyists, these corals from the family Mussidae are an excellent choice for almost any reef aquarium if the following husbandry guidelines are kept in mind.

Acans in the Wild

Acanthastrea species are most frequently observed in Australian waters as flat, massive or encrusting colonies. While some colonies may encrust large areas and stretch for many meters across, others are much smaller and made up of only a few polyps. Regardless of size, all acans share the common trait of possessing meaty polyps that cover the animal’s skeleton. In many cases this makes identification down to the species level virtually impossible.

The polyps of acans host zooxanthellae, and, as such, acans are indeed photosynthetic corals. They also possess, however, aggressive feeding tentacles that are extended at night allowing them to capture food from the water column. The animal’s efficiency when it comes to feeding may well account for its relatively rapid growth rate when compared to other corals with large polyps.

Aquarium Husbandry

Acans make fantastic corals in the aquarium due to their adaptability to a wide range of conditions. Perhaps the most important thing an aquarist can do for an acan specimen is feed it frequently. Frequent feedings (as many as several times a day in an aquaculture setting) can result in extremely rapid growth rates. When it comes to feeding, most acans will readily feed on small (or minced) bits of meaty seafood like mysis, brine shrimp, silversides, table shrimp, etc. They will also accept zooplankton substitutes such as the commercially prepared foods designed for corals and other filter feeders.

If a newly introduced acan specimen is not feeding, the aquarist can “train” the animal by target feeding about an hour after the system’s main lights have gone out. Make sure all the powerheads are turned off so that the food can settle onto the acan’s polyps. Allow about an hour for the food to be recognized and consumed and then turn the powerheads back on. After several nights of doing this, the aquarist should be rewarded by the acan extending its feeder tentacles itself when the lights go out in anticipation of a meal.

As mentioned above, acans are very effective feeders. They are also very effective at defending themselves and even going on the offensive against adjacent corals. As such, it is absolutely essential to give acans a healthy buffer zone of up to six inches (or more). In addition to adjacent sessile invertebrates, acans are known to capture and consume small fishes (such as small gobies).

In terms of lighting, while acans are photosynthetic, they tend to be quite tolerant of a variety of lighting systems. Perhaps the most detrimental thing the aquarist can do to an acan in terms of light is to photo-shock a new specimen by exposing it to lights that are too bright. As is the case with most corals, the animal should be introduced low in the aquarium and gradually moved up to its final position. Many of the Aussie acans are collected in shallow water, and they do well in aquaria with high intensity, reef-ready lighting (although they should not be placed near the top of the tank in such systems). Under weaker lighting systems (e.g., power compacts), they may be placed closer to the top of the aquarium.

In terms of flow, acans are again remarkably tolerant. They tend to be found in protected areas in the wild, so it is best to avoid high flow placements in the aquarium, but they will adapt to a wide range of flow regiments.

Conclusion

Overall, Aussie acans are aquarium favorites and for good reason. They are beautiful and highly suitable for the marine aquarium. If he or she follows these basic guidelines regarding husbandry, almost any reef aquarist can experience success with these amazing corals.