Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of aquatic invertebrate animals, nearly all forming sedentary colonies. Typically about 0.5 millimetres (1⁄64 inch) long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia.