Common Name: Acropora Crab
Bristleworms range in size from small (about 1" long) up to very large at about 20" in length. Most
small ones are an orange color,
sometime appearing two-tone in color. Larger bristleworms are
frequently gray or brownish in color. Bristleworms are composed of
many segments and have bristles (setae) which extend from both sides of
its body along its entire length, hence their common name. These
setae are clearly visible in the picture above. Bristle worms live in the sand or
within the live rock. They are nocturnal and not usually seen during
Good or Bad?:
This is a tough one. Historically, bristleworms were all considered
to be bad. Most literature warns that they can attack and eat clams,
anemones, corals and even fish.
Recently, most hobbyists have come to the conclusion
that small bristle worms pose no threat to other tank inhabitants and are
in fact good scavengers and add to the biodiversity of the tank. You
can even buy bristleworms from some sources.
Even large bristleworms are starting to be better
understood. Although it appears that some large bristleworms can be
aggressive predators, these seem to be in the minority. Many
large bristleworms seem to fall into the harmless scavenger
category. The one in the picture above has
been in one of my tanks for several years. It is about 1/3"
across and at least 12" long although I have only seen about 6"
of it. It lives next to a group of clams and has never shown any
interest in bothering the other creatures in the tank. He is a very
impressive looking specimen in his own right.
Look for bristle worms at night with a flashlight to see if they are
present in your tank. Feeding the tank in the evening will sometimes cause
them to come out and feed.
Capturing large bristleworms, if you desire to do so, can be difficult. They are
secretive and primarily nocturnal. Large ones should not be captured by hand due to
their sharp pincher teeth and setae which can puncture the skin. One
way to capture large ones is to place a rock with a hollow on the bottom side
onto the sand in the evening. A piece of shrimp or similar can be placed
into the hollow to act as bait. The next day the rock can be removed and
the worms will come out with the rock, or they can be captured using a net or
tweezers and disposed of. There are also traps available on the
market. Biological controls are sometimes mentioned. Several species
of Wrasses, Copperbanded Butterflyfish, Banded Coral Shrimp and Arrow Crabs are
all suppose to eat bristleworms, but I doubt that they will eat the large ones
which are the only ones to possibly be concerned about. My recommendation
is to leave them alone unless you have reason to believe they are causing
damage. Also be aware that when an animal, such as a clam dies, the
bristle worms will frequently feed on the carcass as will any scavenger.
Many people misunderstand that the worms are only scavenging and falsely assume
that the worms killed the clam or other specimen.