Large bristle worms

Question
Jennifer,
I recently noticed a large (10-12 inch) bristle worm in my tank.  It seemed to be emitting something into the water and I am concerned.  My tank is full of corals and I am afraid it may damage something.  I have tried to catch this worm on several occasions, but he is too quick. Is he okay to leave in the tank?  It is an established aquarium (6-7 years) and I guess he has been in there for a while.  I only notice him about once a month.

Answer
Hi Ramona. Your common bristleworms can reach lengths of up to 18 inches. Even though they can get this large they are still harmless scavengers. There is one species that gets to be about 12 inches that preys on corals and should be removed with a bristleworm trap. This species is rare and has very distinct coloration. They also do not reproduce in an aquarium. The common bristleworms(harmless ones) are usually pink, pinkish-orange or tan with white bristles on each side of segments and pink or orange gills located above each bristle tuft. The species that will prey on corals is distinctively dark red and silvery grey in body color with blood red frilly gills above each tuft of bristles. It also has a distinct frilled appendage or beard on the back of the head. If this creature has been in your tank for as long as you have had your tank and none of your corals have suffered then it would be safe to assume it is one of the common bristleworms and a harmless, although rather large, scavenger. If you are still concerned then you may want to look into buying a bristleworm trap. Usually these traps are set at night with a piece of meaty marine food and it may take several nights to catch the creature you are intending to dispose of. Never pick up a large bristleworm with your fingers. They are dangerous to the touch and their bristles are venom tipped which can deliver a painful sting.