First thing to note: These guys are good guys… As long as you keep the numbers in check, they don’t get too big & you don’t have a clam!
Bristle worms are probably the most common reef tank critter, most aquarists will encounter them at some point in the hobby. The first time you see a pinky brown, spiked/hairy looking worm pop out of your live rock, your heart will probably stop for a second. These guy’s are not the prettiest of creatures!
There are creatures that look very similar to bristle worms, such as fireworms & bobbits, if you have a fireworm or a bobbit, then you should probably be worried, but bristleworms are generally considered good guys.
Bristle worms can grow up to 24cm long, you should not leave worms anywhere near that size in your aquarium. Once they get to about 10cm long, removal should be considered. This can be done with a set of tweezers or with a trap. You should not handle a bristle worm, the spikes they have will penetrate your skin and will likely be very uncomfortable.
Bristle worms can be a great part of your clean up crew, they can eat left over foods, detritus and fish waste that is deep within your rock and sand bed, that other critters struggle to reach.
Some aquarists will report that a bristle worm has eaten one of their fish, but it is likely that the fish was already dead or very sick. The larger specimens can be more predatory, which is why it is advisable to remove larger ones from your aquarium.
If you have clam, bristle worms need to be removed from your tank, their spikes can irritate the clams foot causing it to close up.
How do you control the numbers?
There are several ways of helping to keep your bristle worm population in check.
Firstly, the more food there is available to them, the quicker they will reproduce, so cut back on your feeding if you feel you are getting too many of them.
Manual removal with a trap or tweezers is also advisable if you have a particularly large worm, or have too many of them. You can find purpose built traps at several online vendors, or watch videos on YouTube on how to make a bristle worm trap.
You can also employ a predator for your tank. There are a number of species that will actively hunt bristle worms, though care should be taken that any new additions are compatible with your existing inhabitants.
Do they have any predators?
There are several bristle worm predators. They include;
- Several Wrasse species are known to predate on bristle worms, including; Six Line Wrasse’s & Sunset Wrasses.
- Arrow Crabs, these are not generally considered reef safe though.
- Dottybacks, can become tank terrors,
- Hawkfish, will eat smaller fish & shrimps along with your bristle worm population
Not all of the species listed above are considered reef safe. Care should be taken when adding livestock to take care of a pest problem. Once they have eaten all of the pests, they will need supplementing with other foods, or they will need to be re-homed. It is for this reason that using a predator to take care of a pest problem, should be your last resort.
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Hah, your description of my feelings on first sighting a bristle worm is spot on!
We are indeed very new to reef tanks, and these pages seem quite helpful. Thanks for the clear pictures and information about the differences between bristle worms and fireworms, I’ve been a little worried!
You do note that when bristle worms get bigger they should be removed. Do they become predatory as they get bigger? Or are they strict detrivores? They definitely come out at feeding time! We’ve seen one or two that I would say are over 10 cm long and over a centimetre wide.
Thankyou for the info. on these worms. Yes my heart did stop for a second or two when I saw it perched on a rock in my aquarium. Thanks to this article I can kind of sleep tonight. Going to get one of those traps tomorrow 🤪.