I have some of those as well, and I always thought from looking through pics that they are P. psammaphila. Mine eat fish food, frozen meats, anything. Put them on the bottom of the tank in a pretty shaded area, and cut on a 14-20k. They are so green it is beautiful!
Thank you everyone! Mine actually sit about 8 inches from the surface and I'm using 14k 250W metal halides. They are huge and eat constantly. Working with these types of animals is new to me. I've always dealt with coral and fish. Again thank you!
That close to the surface, I bet they are just bleached out a bit, and will regain their vibrancy by moving them to less intense light. It's like being on Mars kinda for them...