That's a menella, and yes, they are strictly nps.
Your's doesn't look too bad. I've found menella not to be too difficult, but if tissue recession does occur, keeping algae off can be a struggle (true of any gorg). I've cut the tips of branches off, or, in case of losing the algae battle, I'll completely cut branches off and remount. My small gold menella,in front of the blueberry gorg, was originally about the size of yours... I cut off the remaining healthy branches after battling algae on it for 1.5 years (I've had tissue recession when letting water parameters get off... high alk, phophate, and salinity have all been culprits). Once algae takes hold, it seems hard for them to regrow tissue, otherwise, I see healthy gorgs regrow tissue at rate of 1" in a week.
That's good sign it's open, although, a very healthy one will have "fuzzy" appearance. Any meaty food in the water column should entice it open... they don't open necessarily because it's dark. My large yellow menella stays open most of time, including the during day, while my large, purple one tends to be closed during the day and open with food in the evening (remaining open throughout night).
They eat zooplankton and not phyto-plankton... I recommend target feeding with reef roids and smaller micron size frozen food such as rotifers. Anecdotally, I've read people keeping with just reef roids (or similar). If it seems to be opening less-and-less, then it's not getting proper food and action should be taken... letting it stay closed makes it more and more difficult to get them to open.
