Bristle worms are ugly and intimidating creatures that can get into your tank without you noticing.
Some species are disastrous and can quickly become a hobbyist’s worst nightmare.
Fortunately, some fish and invertebrates have a big appetite for bristle worms and wipe them out before they get a chance to overrun your tank.
Read on to find out about the good and bad species of bristle worms, what eats them, and other methods for removing them.
What Eats Bristle Worms?
Fish and invertebrates that hunt bristle worms down and eat them include Arrow crabs, Coral Banded Shrimp, Wrasses, Flame and Long Nose Hawkfish, Orchid Dottyback and Neon Dottyback, Gobbies, Copperband Butterflyfish, Goatfish, Horseshoe crabs, and some Pufferfish species.
One of the safest and easiest methods for eliminating the bristle worm population is introducing their natural predators into the tank.
You may be wondering why some of your existing carnivorous fish won’t eat the worms.
The truth is that they do, but only if a worm swims right in front of them when they’re hungry enough.
Since bristle worms only emerge at night when your predator fish are asleep, they won’t get a chance to eat them.
However, some species have an appetite for bristle worms and are willing to go around looking for them in the substrate and rock cracks.
Here are some of them:
1. Arrow Crabs
Arrow crabs, or spider crabs, are among your best options to keep the bristle worm population in check.
They’ll go around the tank searching for bristle worms to eat.
One problem with arrow crabs is that they may attack your smaller, slow-moving fish if they get hungry enough.
However, if the worm population is large enough for the arrow crabs to stay full, you won’t have a problem.
They also don’t get along with invertebrates like coral banded shrimp, so don’t mix the two species in a tank.
2. Coral Banded Shrimps
Coral banded shrimp, or banded prawns, are valuable predators that can eradicate bristle worms quickly.
They grow to about three inches.
Their species include the red and white coral banded shrimp, the yellow, blue, purple banded coral shrimp, and the golden coral banded coral shrimp.
This shrimp is unlikely to attack a fish because even slow-moving fish are relatively faster than them.
You can keep them in both saltwater and reef tanks.
Some species of wrasses, like the Six Line wrasse, can be your next best option.
Wrasses live in reef tanks and saltwater tanks, but they need plenty of hiding spots.
Make sure that you feed the wrasses well after the bristle worm population is under control.
Otherwise, they can get aggressive towards other mild-mannered fish or attack tiny invertebrates.
Here are other wrasse varieties that have an appetite for bristle worms, along with other aquarium pests:
- Yellow Coris Wrasse.
- Melanurus Wrasse.
- Sunset Wrasse.
- Maori Wrasse.
- Bird Wrasse.
Hawkfish will also go after bristle worms.
They’re semi-aggressive reef-safe fish that will also attack small invertebrates.
The flame hawkfish and long nose hawkfish will work the best.
You can put them in reef tanks.
They’re semi-aggressive and pick at pests.
6. Other Species that Will Eat Bristle Worms
- Copperband Butterflyfish.
- Horseshoe Crabs.
When deciding on introducing one of the predatory creatures into your tank, research them first and make sure they’re compatible with your tank’s environment and inhabitants.
You don’t want to turn your beloved fish into a snack!
Plus, consider the size of the bristle worms.
If they’re big enough, the tables may turn, and the shrimps, crab, or predatory fish might fall prey to the bristle worms.
What Are Bristle Worms?
Bristle worms, also known as Bristleworms or polychaetes, belong to the Phylum Annelida family.
There are more than 8000 species of bristle worms living all around the world.
About 98 percent of the varieties live in salt water, and fewer than 200 species come from fresh water.
Their characteristics tend to vary from one family to another.
They’re free-living creatures, meaning if you cut them into two parts, each one can live along as an independent survivor.
Bristle worm species vary in size from microscopic varieties to 10 feet in length.
Most marine aquarium worms are around 0.5 to 8 inches.
They have cylindrical segmented bodies, with a pair of leg-shaped parts named parapodia attached to each segment.
In the larger varieties, the parapodia work as respiratory organs.
The smaller bristle worms breathe through their body surface.
These worms have small bristles named chaetae on the segments of their body.
The bristles may seem soft, but they’re actually very hard and sharp.
The worms’ heads are highly developed with large brains and nervous systems.
They have two or four eyes on their heads along with a pair of antennae.
Some have highly developed eyes with lenses, some can only distinguish light and dark, and some are completely blind.
Types of Bristle Worms
The term “bristle worms” can be somewhat confusing when it comes to fishkeeping because it applies to both good and bad species.
To explain this further, let’s divide them into two sections:
1. Common Bristle Worms — The Good Guys
Although these little guys may seem creepy and dangerous, they’re not.
They’re actually beneficial for your aquarium’s environment.
Since they’re scavengers, and not even picky ones, they’ll serve as your dedicated clean-up crew in the tank.
Much like shrimp and snails, they feed off anything dead and rotting.
Bristle worms can go through substrate and rocks and get to places where other waste management crew members can’t.
They eat debris, residue, algae, fish waste, leftover fish food, dead leaves, and rotting animals.
This way, they help decompose the waste that would otherwise turn into harmful ammonia.
The common bristle worm can co-exist with the other inhabitants and won’t hurt or attack other creatures in the tank.
You may see them feeding off a dead fish, but that doesn’t mean they’ve killed it.
They’ll only get close when the fish is dying.
If you’re worried that they’ll multiply and overrun your tank, you should stop overfeeding it.
Bristle worms reproduce when food sources are plentiful.
Therefore, remove any leftover fish food and clean the substrate off debris and detritus.
2. Fireworms — The Bad Guys
Fireworms are unwelcome and destructive guests in an aquarium.
They have hollow bristles that contain toxins inside.
When they touch you or another marine animal, the bristles get stuck in the body and release the toxin, causing a painful and burning sting, much like fire.
They can injure the fish in an aquarium, leaving open wounds and scars that will easily become infected by bacteria and fungus.
The disaster doesn’t end here!
Of the more than 120 fireworm species, some of them are extremely aggressive and predatory.
They’ll attack, bite, and kill fish, invertebrates, and corals if they get big enough.
They have strong jaws that can bite off the corals to their core.
They come out of hiding at night and attack the fish when they’re sleeping.
They’ll even bite you if they get a chance!
Although having them in an aquarium isn’t common, it’s possible, and you should remove them before they get a chance to reproduce.
How to Identify Bristle Worms
To identify a bristle worm, you should get it out of its hiding spot first.
Since they’re nocturnal creatures, you should turn off the lights and wait for them with a flashlight.
They can’t see the red light, so create a red hue with your flashlight.
Once they come out, inspect them for these signs:
They’re common bristle worms if they have less pronounced bristles with a pink, gray, or white body.
If they have evenly spread bristles with white tips and red bases, and the filaments along their bodies are brown, red, yellow, green, or gray, you’re dealing with fireworms.
A bristly worm may emerge out of nowhere at feeding time one day.
A worm that behaves this way is probably a carnivorous fireworm.
You can also look for signs of bitten and chewed off parts on your corals to determine you have a fireworm.
Other Methods to Get Rid of Bristle Worms
Prevention is the best and safest way, especially when it comes to your tank’s health.
Whenever you buy new pieces of live rock, inspect them carefully for signs of bristle worms.
You could have a small, temporary tank, just for keeping the new rocks.
This way, the rocks will stay alive and healthy, and you can inspect them for worms.
2. Manual Removal
This method is a good option if there’s a small population of bristle worms in your tank.
Using a pair of clean tweezers, pick them up one by one by the middle part of their body.
Remember to wear gloves so you don’t get stung.
Another option is to prepare a bucket of dechlorinated fresh water, remove the stones and sediment from the tank, and put them in the bucket.
The sudden change will shock the bristle worms.
They will come out of their hiding spots and fall off to the bottom of the tank.
After a while, you can pick up the rocks, recheck them for any survivors, and put them back inside the tank.
- Simple Food Trap: You can put a piece of cooked shrimp, raw fish, scallops, clams, or other meaty snacks for the bristle worms in the tank at night. When they come out of hiding to eat the treat, you’ll be waiting with a net and a pair of tweezers.
- Hollow Rock: Find a rock with a hollow at the bottom. Place a meaty treat inside it and put the rock on the substrate. The bristle worms will come to the hollow to eat. Remove the rock very fast and use a net to catch the ones that escape.
- Available Trap: There are ready-made bristle worm traps you can buy from your local pet store. Their design allows the worms to get inside easily, but they can’t get out. You’ll just have to put a food bait inside.
- DIY Trap: You can make a trap for these hitchhikers with a small water bottle and straws. Pierce the sides of the bottle and fit the straws in the holes. Put a piece of meat inside the bottle and bury it in the substrate.
Frequently Asked Questions
1. Can Bristle Worms Kill Fish or Corals?
Common bristle worms won’t attack and hurt fish or corals.
They’re scavengers, so they’ll feed off dead coral tissue and the decaying bodies of other dead marine animals.
However, some predatory bristle worms, named fireworms, will attack and bite healthy fish and corals.
They mostly attack smaller fish at night when they’re sleeping.
2. Are Bristle Worms Dangerous to Humans?
If you touch a common bristle worm, the tiny sharp bristles will pierce your skin.
It’ll sting and irritate, but you shouldn’t rub the surface because the fine hair is hard to see and remove.
Use a piece of tape and dab the area to get rid of the pieces.
The bristles of a fireworm are hollow and contain toxins, so your hand will burn if you touch one, much like a bee sting.
Place the injured area in warm vinegar and let the bristles dissolve.
Some predatory fireworms can even bite your finger!
If you suspect that your tank is infested with bristle worms, always wear gloves when putting your hand inside of the water.
3. Are Bristle Worms Parasites?
Common bristle worms can’t be identified as parasites because they feed off the leftover fish food, waste, and detritus.
They won’t eat the fish’s food or hurt them.
4. How Do Bristle Worms Get in Your Tank?
Bristle worms are tiny hitchhikers that you’ve brought to the tank yourself.
They usually hide in live rock or live sand, get into the aquarium environment, and start multiplying.
If you’re worried about their numbers getting out of control, stop overfeeding the fish and remove the leftover food, so the bristle worms don’t get a chance to build a colony.