Commonly called the Thread Worm or Spaghetti Worm. Most of these worms usually conceal themselves in the sand or a crevice in the rock, and live inside a chitonous tube surrounded by grains of sand. Their body remains hidden inside its tube, yet numerous thread-like filaments are fed out into the surrounding water to trap food. Very small food particles/detritus stick to the filaments where cilia on its thread-like tentacles draw particles of matter to its mouth. They are basically harmless detritivores and interesting to watch. Found both in the Indo-Pacific Ocean and Caribbean and are valuable additions to most sandbeds.