If you have bristle worms in your saltwater aquarium and you’re not sure what to do, you’re not alone.
There are a million questions floating around online about bristle worms by new and experienced reef tank owners.
Are they good or bad for your tank? What is a bristle worm vs. a fire worm? How do you get rid of them?
The list goes on and on.
That’s why we’ve put together this resource to answer all of your bristle worm questions. You’ll find everything you’re looking for and be ready to deal with them when you’re done reading.
What are bristle worms?
Bristle worms (polychaetes) are segmented worms that make up the Polychaeta, which is Latin for «many hairs,» class of animals. They belong to the Annelida phylum, which includes more than 22,000 species of ringed and segmented worms.
Earthworms and leeches are also included in this phylum, so think of the bristleworm as a type of marine earthworm.
Of the more than 10,000 species of bristle worms, also spelled, more than 98 percent live in saltwater. Fewer than 200 species live in fresh water. Ranging from microscopic in size to over 50 feet in length, bristle worms are found throughout the world in habitats that range from cold to hot.
Most aquarium species are 3 to 8 inches long, although some can grow up to 2 feet.
The cylindrically segmented body of the bristle worm features a pair of fleshy leg-like appendages known as parapodia on each segment. In addition to a means of movement, the parapodia serve as respiratory organs in larger species.
The smaller species, however, breathe through the general surface of their body. The segments also include bristles known as chaetae which are made up of a material that forms the exoskeletons of arthropods.
The bristle worm’s highly developed head features two to four pairs of eyes that can usually distinguish only light from dark. However, some species are completely blind, while others have large, more developed eyes with lenses.
Also found on the head are a pair of antennae, appendages known as pedipalps, and a pit-like nuchal organ that helps the animal detect food. The mouth, which includes a pair of jaws and a pharynx, is located below the head.
Although simple, the bristleworm’s circulatory system is relatively well developed for an annelid and consists of two main blood vessels, along with smaller vessels that supply blood to the digestive system and the parapodia.
Because most species have blood vessels that constrict to move blood, a heart is not necessary. Some species, however, have muscular pumps located throughout the system and others have no circulatory system at all, but instead move oxygen within the coelomic fluid through their bodies.
Located on top of the head, a relatively large brain is central to the worm’s nervous system, which includes a single or double nerve cord running the length of its body and groups of smaller nerve cells and nerves found in each. segment..
Bristle worms are divided into two orders: wandering and sedentary. As their name suggests, sedentary worms move very little and live in tubes or are burrowers. Their special types of appendages give these “lazy” worms the ability to wait to catch food until it passes by. Vandering species move using their parapodia.
Bristle worms vs fire worms
As you may already know, there is a difference between bristle worms and fire worms. To make it simpler, fireworms are a kind of bristle worm.
The reason why it is so important to understand the difference between them is simple, one can help your aquarium and the other can harm it.
Let’s explore the difference!
Which ones are beneficial for your fish tank?
The bristle worm may look like it came straight out of a Creepy Crawlers Thingmaker, but don’t let its appearance intimidate you. Aside from their prickly bristles that feel like a bee sting when you touch them, most bristle worms are harmless. Because they are scavengers, the «good» bristle worms can actually clean your tank, only snails and some species of starfish can.
That means these types of bristle worms can be an aquarist’s best friend!
The beneficial species of bristle worms are very slender and can fit into small cracks more easily than other scavengers. They are certainly not picky eaters and will eagerly consume anything from food scraps to algae and leaves, dead animals and even fish feces. Most bristle worms also feed at night and prefer detritus.
If you are concerned that your tank may be overrun by bristle worms, even beneficial ones, be careful not to overfeed them. Their rate of reproduction is based on the amount of food they eat, so the more they eat, the more they will reproduce.
Beneficial species come in a wide variety of colors, from dull gray to pink to bright hues. Their evenly spaced, bright white bristles are not as prominent as those of «bad» bristle worms.
Which ones are bad for your tank?
Bristle worms in the family Amphinomidae, known as fireworms, have hollow bristles containing toxins that burn when touched. There are fireworms native to the Pacific and Caribbean regions.
Unlike bristle worm species that feed on dead animals or food scraps, fire worms are carnivorous and attack small live fish, often when the fish are asleep. They will also readily consume invertebrates such as mollusks and crustaceans.
One species, the bearded fireworm, is especially fond of corals. Unlike beneficial bristle worms that wait until dark to feed, the fireworm will feed at any time of the day or night.
Fireworms are usually larger than other types of bristle worms and can grow up to a foot long. They are also brighter in color and can be found in shades ranging from gray to red to yellow to green. Its red-based, white-tipped bristles have short tufts.
Unfortunately, fireworms can reproduce at rates as high as beneficial bristle worms. This means that if you are not paying attention to your tank, fire worms can show up and become a problem very quickly.
How do bristle worms get into your tank in the first place?
If your tank contains live rock, it probably already contains beneficial bristle worms. The creatures are notoriously good at hitchhiking on live rock, so you get an additional house cleaning machine when you buy live rock for your tank.
How to get rid of them?
Unless they breed too profusely, you don’t want to get rid of the beneficial bristle worms in your aquarium. However, if you find that fireworms have invaded your tank, you must remove them as soon as possible to protect other living things.
Option 1 – Find out what the bristle worms eat and introduce them to your tank
One way to eliminate fireworms is to introduce their natural predators to the tank. Some species you might consider adding are arrow crab, hawk, dottyback, certain species of wrasse, coral banded shrimp, and some species of butterfly fish and puffer fish. Introducing these animals to your tank is not only one of the safest ways to get rid of fireworms, but the last two species will add so much to the beauty of your aquarium.
One group of valuable predators is the banded coral shrimp, which includes the red and white banded coral shrimp, golden coral shrimp, yellow banded coral shrimp, and blue or purple banded coral shrimp. Also known as banded shrimp or banded cleaner shrimp, the coral banded shrimp is not technically a true shrimp. Ranging from 2 to 4 inches in length, the Coral Banded Shrimp will eagerly consume bristle worms, but is not a threat to fish.
Another natural predator of the bristle worm is the arrow crab, also known as a spider crab because of its exceptionally long legs. However, you should be careful when introducing this crab to your tank if you already have coral-banded shrimp, as it can attack these crustaceans as well as small, slow-moving fish.
A colorful active fish, the six-lined wrasse, also known as the six-striped wrasse, features six horizontal blue lines that contrast with its orange body. However, in addition to its liking for bristle worms, this fish can attack small crustaceans and other peaceful fish, especially if it is very hungry or lacks a suitable environment in which to hide. The hawk is another natural predator of bristle worms. This fish is usually motionless and unfortunately can also grab any small invertebrates that pass by.
Although introducing natural predators is generally a safe way to remove unwanted bristle worms from your aquarium, be sure to choose a species that won’t harm the other animals living in the tank.
Option 2 – Use a Bristle Worm Trap
If your tank doesn’t have room for more fish, you can try a store-bought or homemade trap to catch fireworms. If you prefer to make your own simple trap, simply cut off the top of a plastic water or soda bottle at the neck. Then flip the cut part over and glue this piece to the top of the bottle, creating a funnel.
Fill the bottom of the bottle with food as bait and bury it upright in sand on the floor of the tank. The bait will attract the fireworms, which will go into the bottle and won’t be able to get out.
Ladies, here’s a practical reason to hang on to your nylon stockings that have been ruined by runs or snags. Use them to make a simple bristle worm trap! Wrap a piece of fresh food, such as a scallop or shrimp, in the stocking and allow the trap to sink to the bottom of the tank.
The worms will be attracted to the food; and when its bristles come into contact with the nylon, they will stick and cannot escape.
The nylon stocking method is especially effective at catching smaller worms. Now you can dispose of the stocking, knowing that it has another purpose!
You can also buy one if you don’t want to go the DIY route. Here is a link to a very reliable and well-reviewed bristle worm trap made by JT Aquatics.
Option 3: Dig around your tank and hunt them down!
There are other methods to remove fire worms from your tank. You can try grasping each one individually by the center of its body with tweezers; but if your tank is inundated with worms, this process can be tricky and time consuming. You also need to remove the entire worm because if part of the animal breaks off and remains on the live rock, it might actually regenerate.
If you suspect fireworms are hiding, you can remove pieces of rock or sediment and immediately place them in fresh non-chlorinated water. The worms will quickly expel the rock or sediment. However, use this method only as a last resort, as other creatures living in the rock could be harmed.
Preventing fireworms from getting into your tank in the first place will save you the hassle of removing them. Carefully inspect all new stone you purchase before putting it in your tank. It could designate a special tank set aside for the purpose of containing the new rock. The rock will remain alive as you monitor it over a period of time. The process may take longer than you’d like, but it’s well worth the extra time it takes to ensure the safety of your main tank.
now you’re ready
You should now have the essential information on bristle worms to deal with them in your tank. You can identify them, remove the fire worms, and make your own decision on whether you want to keep regular bristle worms in your tank.
While there is a lot of confusion surrounding these creatures, it’s really not that bad once you understand the basics.
As always, if you have any questions about bristle worms that we didn’t cover in this guide, you can always get in touch. We are more than happy to help!