The Sea Pen, Cavernularia sp., resembles a quill pen stuck directly into the substrate. It often comes in an orange or tan color. The Sea Pen burrows into the sand and prefers areas with lower water currents. Its upper half blossoms with specialized feeder polyps. It is non-photosynthetic requiring regular feeding. It is a nocturnal species that preys on filter foods found in the tank. Though they don't have any special lighting requirements, the Sea Pen will look absolutely vibrant under nice actinic lights. Overall, this is a wonderful, easy-to-care-for organism that is rather unique.