This coral does contain the symbiotic algae zooxanthellae, which means it uses photosynthesis to create its nutrients. However, I have read that this particular coral should be fed with a product such as micro-plankton.
My second mistake was dropping it on its "face" when I tried to position it in the tank. That it did not like. The polyps retracted and released a coating of slime. I was sure it was a gonner.
I immediately ran out to buy some zooplankton and fed it using a turkey baster. After a few days of nursing it, a third of the polyps came back. Then another third, and finally all of it. It now looks like this.
It is a shocking transformation! It is by far my favourite coral in the tank, and I hope I can continue to keep it alive. By the way, I found that placing it on the sand bed, and away from strong currents works best.
One fascinating thing I witnessed was it releasing some sort of stringy substance from the centre of each polyp. Here is a video.