What type of lighting do you have? They need intense lighting, generally MH to help synthesize energy from the algae that lives in their flesh. This in turn helps feed them. Supplemental feedings can occur in limited amounts using Mysis shrimp, very small pieces of fish or shellfish. Keep in mind it is best to feed in very small portions as ny fodd undigested will be regurgitated into the tank after a few hours and may rot, changing the water parameters.