Whenever the lights are out in my 55-gallon (208-liter)
soft-coral reef tank, a swarm of very small bristleworms
appears, primarily on one side of the tank. Dozens of
them climb up the glass, and I’m also seeing big groups of them
crawling through clumps of hair algae in the tank (yes, I’m fighting
The worms are sort of orange-brown in color, very thin, and only
about a quarter inch ( 6 mm) in length. Any idea why this swarm has
appeared and what fish or invertebrate I can add that might eat them?
San Francisco, California
The fact that you’re battling clumps of hair algae along with
a proliferation of bristleworms strongly suggests to me that
you’ve got a high nutrient level in your system and probably
a lot of detritus in the substrate, which is serving as a food
source for the worms. Lack of adequate water movement, causing a dead
spot where detritus can accumulate, might explain why the worms seem
to be more heavily concentrated on one side of the tank. You might need
to remedy this through the addition of a powerhead, or by redirecting
existing sources of current.
There are certain animals that will help rid a tank of bristleworms,
such as the banded coral shrimp (Stenopus hispidus) and various
wrasse species (e.g., Pseudocheilinus spp.), but I would recommend
that you attack the root of the issue by increasing the frequency and
volume of water changes and more thoroughly vacuuming your substrate
(provided it’s coarse enough that you can vacuum it) before introducing
any control organism, which, after all, will only add to the bioload.
If you reduce their food supply in this manner, you should see the
bristleworm population start to decline proportionately. D
The banded coral shrimp (Stenopus hispidus) is often added to rid an aquarium of bristleworms.