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Is the bristle worm in your aquarium good or bad?

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Bristle worms are found in almost every marine or reef aquarium. But what are bristle worms? Are they dangerous to your fish and corals and do you really want them in your aquarium?

Bristleworms are more complex than many aquarists believe. In this article, we’re going to explain everything you need to know about the worms so that you can decide if you want some of these creepy animals in your aquarium.

What is a bristle worm?

Bristle worms, bristle worms, or polychaetas belong to the class of segmented worms, which means that they are usually marine species. The common name for this type of worm is the bristle worm.

The worm’s cylindrical body is made up of segments, each with a pair of fleshy parts like legs, commonly known as parapods. Each segment also has bundles of chitin bristles called chaetae.

Bristleworms are found all over the world, from underwater hot springs to some of the coldest regions on the planet. Some species of bristle worm drift with the ocean currents just like plankton, while others live in the deepest areas of the oceans. In fact, a bristle worm has been discovered living in Challenger Deep, the deepest part of the planet’s oceans.

Types of bristle worms

There are over 8,000 different types of bristle worms. Around 170 are found in freshwater, the rest are brackish or marine species.

The size of the bristle worms varies from microscopic species that are invisible to the naked eye to other species that are 50-foot monsters. In general, however, most aquarium species measure between three and eight inches. The worms are also available in different colors, with some being luminescent or iridescent.

Bristleworms can be divided into two different orders; flawed and sedentary.

Defective bristle worms

Faulty bristle worms use their “legs” or parapodia to move, crawl or swim in your aquarium.

One type of faulty bristle worm that you absolutely don’t want to find in your tank is the fire worm. The bristles of fireworms can break off into the skin of anyone who comes in contact with the worms, and this can be excruciatingly painful.

Sitting bristle worms

Sedentary bristle worms live in tubes or caves and do not move as much as their erring relatives.

What is good about bristle worms in the aquarium?

Bristleworms are one of nature’s cleaners and eat up decomposing food or dead organic substances in the tank. Despite their small size, the worms can cleanse just as effectively as some species of starfish and snails. In addition, the worms can squeeze into tiny cracks and crevices that other larger members of the cleaning crew cannot fit into. In principle, every organism that contributes to cleaning your tank is welcome.

Often times, bristle worms arrive in living rock so you don’t even have to buy one of these helpful little creatures!

What’s NOT good about bristle worms in your tank?

There are a few types of bristle worms belonging to the Amphnomidae that have hollow bristles. They contain poisonous substances that can cause an unbearable burning sensation if touched, giving the worms the name fireworms.

Some types of bristle worms are also carnivorous, which means that they will attack your fish. If you spot any of these types in your aquarium, you’ll want to get rid of them right away.

How to distinguish the good from the bad

How do you distinguish a harmless bristle worm from a dangerous one?

Bristle worm (polychaete)

Common bristle worms are welcome in your saltwater aquarium and will usually hitchhike into your setup on living rocks. These worms are harmless detrivores that will not pose a risk to your fish, and they will also help keep your tank clean by eating waste food and general debris.

Common bristle worms are thinner than fire worms, with less pronounced bristles, which are usually pink in color.

Bearded fireworm (Hermodice carunculata)

Fireworms and other carnivorous species are generally large and more colorful than their more peaceful, detritus-eating relatives. If you see a brightly colored bristle worm with very well defined chaetes, it is most likely a fireworm.

There are around 120 types of fire worms! All of them have very defined bristles that are usually reddish in color around the base.

The fireworm that has the worst reputation is the bearded fireworm. This species of worm from the Amphinomidae family is carnivorous and will grow in front of corals and saltwater fish and reach a length of up to 30 cm. Bearded fire worms have short bundles of red and white bristles, and the bodies of the worms can be of various shades, including yellow, red, green, or gray.

How do you get rid of bristle worms?

If you don’t like the idea of ​​those bristly wrigglers in your saltwater aquarium, you need to know how to get rid of them.

Natural predators

Fortunately, there are many natural predators out there that will happily devour the bristle worm populations in your tank. This is the most effective, safest, and most environmentally friendly way to get worms out of your tank. Some of the creatures that you can introduce into your aquarium that are older than the worms include:

  • Arrow crabs
  • Sunset wrasse
  • Dottyback
  • Prawns with coral ribbons
  • Maori wrasse
  • Wrasse

Some species of butterfly fish and puffer fish eat bristle worms. Many of these worm-eating creatures are stunningly beautiful and reef-safe, making them a lovely addition to a marine tank.

Bristle worm traps

If you don’t want to add more fish to your aquarium, you can use a bristle worm trap. A bristle worm trap is the next best thing to use natural predators to solve your bad bristle worm problem. The most effective traps are those that allow worms to enter the trap but have no exit.

Although you can buy bristle worm traps, you can easily make one too.

How to make a bristle worm trap

  1. Take a plastic bottle and cut it horizontally across the neck.
  2. Turn the piece you just cut over and glue it on top of the bottle to create a funnel on top of the bottle.
  3. Place a bait in the bottom of the trap and stick it upright in the sand with only the entrance visible.

The idea is that in search of food, the worms enter the trap, fall into the ground, and are unable to climb up the slippery sides of the bottle to get out. Remember to remove the trap and dispose of the worms every few days.

Other ways to get rid of bristle worms

You can remove bristle worms by hand, but be careful not to touch fire worms. Wear gloves and use tweezers to handle the worms. This method can be effective if there aren’t too many worms in the tank.

You can also remove small parts of the substrate and rock and place them in fresh, dechlorinated water. This will encourage the worms to come out of the rock. The main disadvantage of this approach is that you can also damage anything else that lives in the rock or substrate.

This is how you prevent bristle worms from getting into your saltwater aquarium

It is always best to prevent bristle worms from getting into your tank in the first place, rather than getting rid of them once they arrive.

Carefully check all of the live rocks that you add to the tank. You may also want to set up a separate quarantine tank for the rock so that you can keep the rock alive while observing what may be living in or on the rock. Once you are sure nothing is trying to hitch a ride on the rock, you can add it to your tank.


In this section of our guide to bristle worms, we answer some of the most frequently asked questions about these creatures.

Q: Can a bristle worm harm you?

A: It depends on the type of bristle worm. Some fireworms are dangerous to touch and some are not. For safety reasons, always wear gloves when handling bristle worms. The worm’s bristles can break off and irritate your skin painfully. If you are allergic to the toxin contained in the bristles, you can also feel dizzy and sick.

Other than that, bristle worms are not dangerous and will not harm you. Be especially careful when moving live stones or substrates around your aquarium.

Q: What is the difference between a fireworm and a bristle worm?

A: All types of fireworms are also classified as bristle worms. However, not every bristle worm is a fire worm. Fireworms are usually larger than bristle worms and often lighter in color.

Q: Should you eradicate bristle worms from your sea or reef tank?

In most cases, some bristle worms in your aquarium will not be able to harm your fish. That said, some species are predatory, so you need to determine what type of worms you have. This is often easier said than done since the worms are mostly nocturnal so you don’t see them very often.

However, if you spot a large fireworm attacking your fish, you will want to remove it using one of the methods previously discussed in this guide.

Q: W.What do bristle worms eat?

A: In general, you don’t need to worry too much about feeding bristle worms. These creatures are natural scavengers that happily exist on food that drifts down from above the substrate, as well as leaves and algae.

Bristleworms also eat dead fish and other creatures, and some species, like the Christmas tree worm, catch floating food with their special attachments.

Final thoughts

Bristle worms are generally not considered an undesirable inhabitant of your marine aquarium. In fact, these harmless little creatures can help the aquarist clean up litter and general trash.

However, you don’t want fireworms in your tank. Most types of fire worms are bad news and will sting you if you accidentally brush a brush while doing maintenance on your tank. Some of the larger species of fireworms live off fish.

In short, if you want to have some harmless cleaners in your tank, you might want to let the bristle worms stick around. Fireworms, on the other hand, should immediately show the door and be handled with the utmost care!

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