That's diodogorgia nodulifera - non-photosynthetic and not very easy to keep. To keep it healthy, you will need to place it in pretty high flow, keep algea from overgrowing it (by brushing it off, keeping it in subdued lighting, etc), and feed it LOTS of zooplankton. Diodogorgia have fairly large polyps, so prey somewhere around 300-800 microns will do well.