You don't need to feed it, it gets all it needs from the light so don't stress too much about that. I keep two nems and one takes food and the other doesn't. Having said that it doesn't look good at all and it only opens for an hour a day? I could be on the way out I am afraid. Is your tank new? Nems don't like any swings in parameters particularly temp and salinity which is why it's recommended to wait 8-12 months before adding one. Do you keep records of your tests? Do you see any swings in parameters?