Common Names: Fan Worm, Feather Duster Worm
Scientific Name: Various
Hitchhiking fan worms range from very small inconspicuous specimens up to relatively large ones that can extend over an inch across at the crown. Their long segmented body is incased in a leathery tube for protection from which their crown of tentacles emerge to feed by filtering small food particles out of the water. When disturbed, the crown is quickly withdrawn into the tube for protection. The tube is generally partially buried in the substrate or attached to a solid structure such as a rock or the wall of the aquarium. They are commonly white to light tan in color, though sometimes are an attractive pink, light blue or other color. The images of wild colonies below show some of the more attractive colors that they can have, though unfortunately most found as hitchhikers in the reef tank are the basic white version shown on the left below.
They can reproduce in the aquarium and can rapidly colonize areas such as the sump where there are no fish predators and the microscopic food that they filter out of the water is conveniently served to them as the water flows through the sump. They may also colonize the display tank if there are no fan worm predators in the tank or if there are protected areas in the tank where predators can’t reach them.
Good or Bad?
There is nothing ‘bad’ about a fan worm. In fact their larger cousins like the Hawaiian Feather Duster are often sold in the hobby. They exist in virtually every reef tank and earn a living by filtering the water through their crown. Growth and proliferation of fan worms indicates that there is enough floating food particles in the water to support them. Tanks that are feed phytoplankton and similar filter feeding foods or which do not have heavy protein skimming will tend to have more fan worms as will tanks with poor husbandry. Their filtering action should help with water quality if only an inconsequential amount. Fan worms can also be quite attractive additions to the tank. They also can serve as food for other animals such as Copperband Butterflyfish or Wrasses whether intentionally or accidentally.
Some photos courtesy of Nick Hobgood or NOOA and tagged individually. All other photos by ReefCorner and all rights reserved.