Bristle Worms (Good, Bad, & Ugly)

Image Credit: MaMe via Reef2Reef
Image Credit: MaMe via Reef2Reef

Bristle Worms (Good, Bad, & Ugly)


If you are getting into reef aquariums as a new hobby, then you probably have heard of bristle worms before. They are the worms from your aquarium, and you may not know what to think of them quite yet. The little worms are mentioned frequently when discussing tank health and aquascaping. The reason for this is because the little worms can be one of your biggest allies or one of your biggest nightmares. However, it depends on which ones you are dealing with because not all bristle worms are the same. This means it is important to not only know what makes a bristle worm good but also what makes some of them bad.

Are Bristle Worms Good or Bad?

That would depend on the type of bristle worm. As I have already mentioned, bristle worms come in thousands of varieties. Bristle worms depend largely on their type whether they will benefit your aquarium or not. There are also a few things to consider when discussing the inner morality of the bristle worm. I will touch on a few of the things you should keep in mind when assessing whether you have a fireworm or a good worm in your reef tanks.

Before we go any further, if you plan on handling bristle worms for any reason, please wear proper hand protection as some species of bristle worm are toxic.

What do Bristle Worms Eat?

Bristle worms dig in the dirt and mud to find their meals. The food they enjoy is whatever is rotting in the tank and ruining the water for all the other tank inhabitants. This means the good bristle worms will eat the leftover food that can be found in your tank. As food falls in the form of waste and dead fish, bristle worms will come by and begin picking at the offerings. They help to keep the tank clean for your reef fish to enjoy. Fireworms on the other hand will attack live fish and coral causing harm to the overall ecosystem of your reef. You will want to identify these worms and begin to remove them as soon as possible.

What do Bristle Worms do for my Aquarium?

Bristle worms will work to keep the overall health of the tank in check. They will help to keep algae from building up by removing leftover food and waste that would aid in algae formation. In a way, bristle worms can be a great ally to an aquarist. Depending on how your tank is set up, you may not notice some of the things that take place right away. For instance, what if one of your fish passes away and you don’t notice right away?

Team bristle worm will have your back as they begin to pick at the rotting carcass. What this does in the long term is to keep your water within the specific parameters that you have set for your fish. The only trouble is making sure that all the worms present are on team cleanup which means no fireworms. Fireworms will cause damage to the reef life present and potentially cause some serious damage to the health of some of your fish.

You will want to monitor how quickly your bristle worms are reproducing in your reef tank. A sign that something is wrong with your saltwater aquarium is when bristle worm reproduction is excessive.

Do Bristle Worms Kill Coral or Fish?

Unfortunately, there are species of bristle worms that can be a detriment to your coral and fish’s health. The bearded fireworm is a carnivore and you do not want it anywhere near your reef tank. It will attack the fish and coral in your tank. If you become aware of a bearded fireworm in your aquarium, you should try to follow some of the removal practices that I outline below to remove the threat from your tank.

A bearded bristle worm can grow anywhere between 6 and 12 inches and they have various body colors.

Tools For Removing Bristle Worms

Bristle Worm Trap

This bristle worm trap is the best method for removing bristle worms easily.

Long Tweezers

Long tweezers are great for picking out easy-to-reach worms.

Mechanical Tongs

An even longer tool to allow you to pick out bristle worms directly.

Suction Syringe

This giant syringe can suck up bristle worms and other small reef pests.

What is a Bristle Worm Exactly?

Polychaeta, or bristle worms, are a class of annelid worms, or segmented worms and most live in the ocean. They are not the most attractive creatures that can be found in your saltwater aquarium, but they can have a tremendous impact on its overall health, due to their willingness to be the custodians of your aquarium.

Bristle Worms Come in Many Varieties

Bristle worms can be found literally everywhere and have over 8,000 species. There are two orders of bristle worm. Errant worms use parapodia, or their muscular bristle appendages, to move around. The common bristle worm is a part of this order of worm. The common bristle worm can often be identified by its color, which usually is gray or pink. The fireworm, every aquarist’s nightmare, is also part of the errant order of worms. Sedentary worms on the other hand don’t move around too much and typically bury themselves or live in tubes. Since there are so many different types of worms, there are some worms that are a big help to overall aquarium health and there are some worms that cause nothing but trouble for your reef tank. Fireworms are the ones you want to be on the lookout for. They can be easily identified by their bulky body and most have a reddish color on the perimeter of their bodies.

How do Bristle Worms Reproduce?

Bristle worms reproduce by releasing their eggs and sperm into the area around them. The rate of reproduction is enhanced when a tank is supplying the bristle worms with more food than they need. It is a clear sign of something amiss if your bristle worm population is growing. You would do well to clean your tank and double-check your water parameters.

How do Bristle Worms get in Reef Tanks?

Bristle worms usually enter a fish tank on a live rock that you purchase. Bristle worms help to make the live rock beneficial for your tank. The only issue is that sometimes the bristle worms that find their way into your tank are not the ones you want. When this happens, you want to remove the unwanted pest from your tank as quickly as possible.

How to Get Rid of Bristle Worms?

Luckily, there is little reason to have to go out of your way to try to get rid of your Bristle worms. Unless the worms are reproducing too quickly, most bristle worms are more than fine to leave in your reef tank. However, if your tank has a wireworm problem then you might want to step up your removal efforts. You should consider the following options when planning for the removal of bristle worms.

What Eats Bristle Worms?

You can introduce natural predators to eat the pests. It is a great way to keep your saltwater tank in check, and it can also introduce a lot of color and life to the aquarium. As easy as it is for these worms to hitchhike their way into your saltwater tank, it is just as easy to keep natural predators that hunt them when they arrive. There are a wide variety of species that will help keep your bristle worm population in check. You could consider Coral Banded Shrimp, Bird Wrasse, Dottyback, or various types of pufferfish. You just want to double-check that the bristle worm predators that you select will acclimate to the reef ecosystem you have arranged in your tank.

For instance, if you were to introduce an arrow crab into your tank to help fend off fireworms, you would need to keep in mind that these animals also can strike at small fish or even coral. You will want to keep a watch on the arrow crab is properly fed and not hunting any inhabitants of the tank that it shouldn’t be hunting.

In general, for any natural predators, you may add to your aquarium community, it is important to ensure you have a full grasp on their diet and behavior. You do not want to put your fish in potentially more trouble just over a fireworm. Your aquarium will not start falling apart because a fireworm or two got in. However, this does mean you need to be vigilant in noticing any new animals in your aquarium.

How to Trap Bristle Worms?

You might also consider a bristle worm trap which is a great option for aquarists who may not have the space available in their tanks for more predators. The best part about bristle worm traps is that they are largely inexpensive.

You can make a trap with a plastic bottle, a small piece of bait like a shrimp, and tiny holes on the sides. You will want to use plastic tubing to plug up the holes, these tubes will be what the bristle worms will use to crawl into the bottle and get trapped with the bait. The straws should be positioned on your live rock with the bottle nestled in the bottom of the tank. Depending on the number of bristle worms you are trying to get rid of, it may be beneficial to check the trap once a day. A lot of worms can pile into your trap in a short period of time. You may need to take the trap out, empty it, and replace it at the bottom of the tank.

You can also try cutting a small Tupperware container into a trap. The small shrimp bait would still be placed in the center, but this time try cutting small holes at the top and bottom sides of the container. You half bury this trap just like the other one and check back in 12-24 hours.

If creating your own bristle worm trap seems too extensive, you can always buy a premade one. If this is your first time trying to deal with a bristle worm infestation, a premade trap might be your best option for simplicity’s sake.

Last Resort-Dive in Yourself

You can always forgo the traps and predators and try to remove all the fireworms yourself. This method is best done when the tank is not fully populated yet since it can be disruptive to the fish living there. You want to remove each worm in its entirety, if you accidentally split one and it remains in the rock you run the risk of it regenerating. That would defeat the whole purpose of all the work you just went through. You can also remove the liverock that you believe to be hosting some of the bristle worms and place it gently in fresh de-chlorinated water. The worms will not be pleased and leave the rock. The problem with this method is that it is very dangerous to any creatures that might also call that rock home. For large infestations, this method is also not recommended. To save yourself the need to bother your fish, it would be best to try a trap first unless you are positively sure you are dealing with only one or two fireworms.

If you would like more information related to fireworm removal, please check out Reef Tank Resource’s article!

How do You Prevent Bristle Worms?

The best offense is always a good defense when it comes to bad bristle worms. The best way to prevent a bristle worm infestation would be to check all your live rock when you first buy it. You can give it a visual scan when you get it but to be completely sure you might want to set up a temporary space for your new rock. If you have it available, a second tank (or container big enough for water and rocks) just for monitoring rocks and waiting to see what might be living in it. you want to make sure that the tank you use is safe for the good bristle worms that may be living on your rock. You do not necessarily want to remove the bristle worms because that would defeat the whole purpose of purchasing a live rock. You will want to make sure that the conditions of the temporary tank are the same as the final tank that you will be using for your rock. You are not trying to kill off the creatures that may be living on the rock, instead, you are only trying to see if any fireworms are about to sneak into your saltwater tank.


If you came into this post with prejudice against our bristle worm friends, I hope that you can see now that they are not all that bad. In fact, for many people bristle worms are a much-needed teammate in their tank community. Bristleworms can make the job of the aquarists much simpler but at the same time, bad bristle worms can cause you some heartache, if left unchecked. The main job, when it comes to bristleworms, is making sure that the good ones are allowed in and the bad ones get evicted as quickly as possible. Ideally, you will have spotted the fireworms before placing the rock in your tank but fireworms are a determined group of pests.

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