Polychaete bristle worms live in their tube homes in grottos covered with the crust of red Lithophyllum incrustans calcareous alga. Their mouth apparatus looks like a crown of feather-like tentacles (as, for example, these vividly ruddy Protula tubularia have), that is used to filter different organic parts out of the water. Or may be similar to a bundle of thin extended threads (yellow at the picture), like that of Eupolymnia nebulosa, that scrapes benthos with these threads away from vaults and the floor.