Bristle worms are segmented worms from the scientific family Polychaeta. They can live in the most extreme marine environments, from the superheated waters near thermal vents to the coldest and deepest chasms on the ocean floor. They are happy to make a home in your saltwater aquarium.
With more than 10,000 species in the family, bristle worms vary widely in appearance, and their ability to stretch and compress their bodies can make it hard to tell even how long an individual is.
They are recognized by their distinctive chitin ‘bristles’ along the length of their bodies. They are nocturnal and occupy tiny burrows and crevices in rock and wood, so many bristle worms go unnoticed for years.
What do Bristle Worms Eat?
Most bristle worms are scavengers, surviving on plankton, algae, and dead organic matter in an aquarium. They can be very peaceful and efficient tank cleaners, cleaning up waste and leftover food.
A few specific species, known as fire worms, prey on corals, crustaceans, and anemones and can be harmful in an aquarium.
Where do Bristle Worms Come From, and How do They Get in Your Tank?
Because there are thousands of varieties of bristle worms, and they live in nearly every marine habitat, it may be easier to ask where they don’t come from.
They almost always arrive in a home aquarium as hitchhikers on driftwood, living rock, or living sand. When hidden, these worms are practically impossible to spot, and they are easily added to your tank along with other organic materials.
Can Bristle Worms Kill Fish?
They cannot kill fish. They eat dead material and tank debris, so if a fish is already dead, you may see bristle worms on the carcass, which is why some people suspect the worms have killed the fish. However, large fire worms, if left unchecked, have been known to eat small fish.
They should not be allowed to live in a tank with clams or shellfish, but not because they will eat or kill them. The ‘bristles’ will irritate the tender flesh of shellfish, though, and make them close up.
What Do Bristle Worms Do?
They spend most of their time searching tiny crevices in stone and rock, eating algae, plankton, biofilm, and other debris in a fish tank.
The more food available in a tank, the larger bristle worms will grow, and the faster they will reproduce. When bristle worms become a visible nuisance in your tank, it’s a sign that you are overfeeding.
Should I Get Rid of Bristle Worms or Not?
There are several reasons that people usually want to get rid of them:
- They are ugly and creepy looking. Personal tastes vary, but some people are very startled and dismayed to find a big hairy worm in their beautiful aquarium
- They have a worm problem. In a tank with a great environment and lots of food, worms can reproduce and become a problem
- They may have fire worms, not bristle worms. Fireworks can be destructive in a reef tank and should be removed
However, many people have good reasons for keeping bristle worms in their tank and letting them be. Some of the best reasons are:
- They are excellent tank cleaners. The worms’ size and flexibility allow them to reach the tiniest cracks and crevices, cleaning more efficiently than other organisms.
- They reduce ammonia. By consuming organic debris before it decomposes, they keep ammonia levels in an aquarium lower
- They are natural. In any natural seawater environment, there would be bristle worms scavenging and cleaning. When a home aquarist is trying to recreate a natural ecosystem, bristle worms would be part of it
In other words, if you have peaceful, beneficial bristle worms, you can look at them as free tank cleaners who aren’t doing any harm and can be left in peace. If they bother you or are aggressive, they can be removed.
How do I Get Rid of Bristle Worms from My Tank?
When trying to get rid of them, the most important thing to know is that you should never touch them with your hands.
Their ‘bristles’ are defensive features, and the fine hairs will get embedded in your skin, causing severe itching and irritation.
If you accidentally touch one of these worms, remove the bristles with tweezers or adhesive tape, and treat the area with vinegar to neutralize the reaction. Always wear gloves when you have bristle worms.
There are many methods of removing bristle worms and fire worms from your tank. Here are the most popular.
Manually
They are nocturnal (fire worms aren’t so shy and may come out at feeding time, even in the day). Turn out the lights and observe your tank with a flashlight. When you see a worm emerge, grab it with tweezers or tongs and remove it from the tank.
Use a Trap
Commercial bristle worm traps are available, and some of them are very effective. You can also make your own bristle worm trap by taking a very clean plastic bottle. Then cut a small hole in it, place a plastic drinking straw in the hole, place some bait inside the bottle, and seal it.
Put the trap near your aquarium rocks, with the straw resting on the rocks or on your substrate (the end of the straw should not be in open water).
The worm will crawl through the straw into the bottle to reach the bait but will have difficulty finding its way out.
Add a Predator
Many fish species naturally prey on bristle worms, and you may find one that is suited to your aquarium habitat. Beware that most of these fish are not reef-safe and may pose a threat to other inhabitants of your fish tank. Some fish to consider are:
- Dottyback
- Wrasses
- Coral banded shrimp
- Arrow crab
- Some species of pufferfish
- Some species of butterflyfish
Clean Your Living Rock
If bristle worms live in your rock, sand, or driftwood, you can remove them from your tank by submerging them in fresh, de-chlorinated water. This method will also kill or harm the healthy, beneficial organisms in your rock, but it will remove the worms.
The best way to get rid of them is to not have them, to begin with. The easiest way to ensure that your rock doesn’t have any unwanted hitchhikers is to set up and use a quarantine tank before adding anything to your aquarium.
A quarantine tank is a good idea to prevent bristle worms and a wide range of fish diseases and problems in your aquarium.
A quarantine tank gives you an excellent opportunity to observe your new living rock, sand, or driftwood and see if it has any unwanted guests. It can be small but should be cycled and have healthy, balanced water.
Be mindful that bristle worms can be very small, and may feed adequately on organic matter in the rock itself, so you may not spot them immediately. Use a bristle worm trap, or simply place bait in the bottom of the quarantine tank, to see if any worms emerge.
Conclusion
Bristle worms are natural and not necessarily harmful inhabitants of an aquarium. Many people allow them to live unharmed and regard them as healthy tank cleaners.
However, if you want to remove them, there are several ways to trap or kill them or consider adding a predator fish to keep their numbers low.
They are part of the natural ecosystem, and these resilient, versatile little creatures show up in a huge percentage of home aquariums.
Many people have them without knowing it because they are small, nocturnal, and peaceful. If your bristle worms aren’t harmful, consider allowing them to remain in your tank and make your at-home marine environment more natural and balanced.