Bisma Worm Rock, Spirobranchus giganteus, is a type of worm that forms a symbiotic relationship with SPS corals. They are also known as Christmas Worms. Bisma Worms exude brilliant and variegated colors making the rock appear as a shining jewel. They are filter feeders but will benefit from supplemental feedings of particle foods. Bisma Worms should not be housed with predatory fish, urchins, or serpent stars than can attack.