A coco worm is a marine invertebrate related to feather duster worms that lives in a hard, white calcium carbonate tube and has a feathered crown. They are filter feeders, consuming plankton and other fine particles from the water, and require specific care in a reef aquarium, such as stable, high-quality water and supplemental feedings. There is also a coconut worm, a type of beetle larva that damages coconut trees, which is different from the marine coco worm.