When it is feeding the peacock fan worm is like a small feathery flower with a thick straw-like stalk. Depending on the current they may be between 20mm high and 10mm across and 250mm high and 60mm across. The fan worm retracts if it senses danger, a sudden change in water pressure or light level, leaving just the straw-like tube showing. The peacock fan worm has narrow red marks on the feathery fronds of its fan.