Bristle worms (Polychaeta) can sometimes be a surprise when first found in your saltwater aquarium. I know I’d never come across them till I saw one crawling out from a rock on the sand one evening. You can see if you have any in your tank by using a torch and searching the sand for them at night. Most people will try to find out how to get rid of bristle worms as soon as they’ve seen one.
Just a word of warning … don’t touch them. Their fine hairy bristles (called setae) will pierce your skin and cause irritation, much like the fibres from fibre glass . If this does happen, use tape to dab the area to remove the fine hairs. Rinsing the area with vinegar afterwards will clean the area.
Also, do not confuse bristle worms with Fireworms or Bobbit Worms (Eunice aphroditois). These are also a type of bristle worm but are very uncommon to find in aquariums, although not impossible. You would definitely want to remove these worms.
So, on to the topic of this post …
Are bristleworms good or bad?
I would only recommend getting rid of bristle worms if there really are too many of them in your tank. They are great scavengers, helping to keep your tank clean. They could in fact be considered part of the clean up crew in your tank.
Contrary to what some might say, bristle worms will not go on the hunt and catch healthy fish. They will however pick at a fish that is already dead.
If you start seeing more and more bristle worms in your reef tank you may be overfeeding your fish. They will multiply the more you overfeed your tank but will similarly reduce in numbers if there is not enough leftover food for them to eat.
How do I get rid of bristle worms in my tank?
If you find that your tank is being overrun with them, here are two main ways of catching bristle worms in a reef tank:
Make a DIY bristle worm trap from a small plastic bottle with small pieces of drinking straw coming out of the sides. The idea behind this is that the bristle worms find their way in easily but not out. A small piece of meaty food, such as a piece of shrimp, is placed inside the bottle, enticing the worms out of their hiding places.
Place a piece of shrimp or mussel in the tank at night with the flow off. Using tweezers, you can then remove any bristle worms that come out to eat it.
You could also buy a Bristle worm predator (more info below) to try and reduce the amount in your tank.
Can bristle worms kill coral?
Common Bristle worms do not kill coral. They may eat away at dead coral tissue but will never go in search of healthy coral.
Is a bristle worm a parasite?
Bristle worms are scavengers. They eat all the leftover food in your tank once your fish have had their fill. They will not ‘attack’ healthy fish or invertebrates.
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What kills bristle worms?
There are a few fish and invertebrates that will eat bristle worms. Like with anything live you buy for your tank, it is important to find out how compatible they are with your current livestock and coral.
For example, the Banded Coral shrimp are known to have a voracious appetite for bristle worms. But, they can be aggressive towards fish. Arrow crabs are a good choice for keeping bristle worm populations in check however not all arrow crabs will eat them.
With regards to fish that enjoy them as a meal, Flame Hawkfish and Six Line Wrasse are good options but again, check their compatibility with the rest of your fish, invertebrates and coral.
Wrasses can attack and eat invertebrates if they get too large. I had a wrasse which was great in the 4ft tank. When I got the 5ft tank, she grew ALOT and caught her nipping the tail ends of the two fire shrimp. They were healthy and still alive when she did. We had to unfortunately catch her and move her on.
Where do they come from?
Bristle worms are hitchhikers. They are usually introduced to your tank, unknowingly, when you purchase live rock or live sand.
For more info on hitchhikers and many other topics, download our ebook on successfully setting up a saltwater aquarium.
Can bristle worms kill fish?
Bristle worms are not known to eat healthy fish. They will however make a meal of a dead or dying fish.
Bobbit worms however, will eat fish although it is very uncommon to find one in saltwater aquariums. These predators are found in the sand whereas Fireworms and the common type of Bristle worm are found mainly in rockwork or hiding in the folds at the base of a clam.
Bristle worm or Fireworm?
Fireworms cannot be confused with the common bristle worm (Polychaete linopherus) most of us have in our saltwater aquariums. They are quite distinctive with their bright orange rings around the bristles.
Getting stung by a Fireworm is far worse than being stung by a Bristle worm so extreme care should be taken if you happen to find one in your tank and try to remove it.
Fireworms will not only feed on coral and invertebrates but also clams and anemones. They can grow up to 35cms long although they are sure to be smaller in an aquarium as opposed to the ocean.
Unlike common bristle worms, these are definitely best removed.
Below is a great video of a Fireworm.
So there you have it!
I would not get rid of bristle worms unless there were too many of them in my tank. They are good scavengers that help to keep the aquarium clean.