its a pink suncoral it is non photosynthetic and needs to be fed meaty foods every few days or daily if possible.
spray some juice from your mysis near it and then give them ten mins to come out , once out feed the mysis itself to every polyp.
these corals can be placed in pitch dark but need good water quality and they absolutely need to be fed , the more you feed the faster it grows
hth
cheers
denny