Bristle Worm: Are they good or bad?

Ever wondered what an underwater centipede looks like? Well go no further, here we have the Bristle Worm. They are worms that come from the Polychaete family, they are segmented worms and they love to spend their life in the dark. Yes, they are nocturnal creatures.

Bristle worms can be found in salt water aquariums and there are mixed claims about them. Some people claim they are good for the aquarium ecosystem because they tend to eat food that fish leave behind and they clean the aquarium just like an algae-eater, but some people consider them to be pests that need to be eliminated.

In Latin, this creature can be called “hairy worm” because the word Polychaete actually means “many hairs” and by the looks of the creatures there is no objection why the people who first discovered it settled on that name.

bristle worm

What actually is a bristle worm and how it affects my aquarium?

Currently there are almost 10.000 species of these worms, some of which live inside our aquariums. They have been classified by aquarists in 2 easy categories: the good worms and the bad worms.

What is interesting about these worms is that their size is hard to be determined. We can have a 8 cm bristle worm that can elongate up to 20 cm or even shrink down to 4 cm! This way they can fit in small holes and can easily move between aquarium decorations making them hard to spot.

Bristle worms find their way into our tanks when we introduce new natural decorations such as rocks and wood that have not been efficiently thermal treated (it is recommended that you boil every natural decoration that you want to introduce in your aquarium, this way you avoid a wider range of parasites, not only bristle worms).

Having one or two of those worms in the aquarium does not pose a problem, they will help by doing the clean-up job. But when their population exceeds more than 5 individuals you know there is something wrong and it needs to be fixed. Bristle worms multiply when they find a good food source, so if you have a lot of dead fish and wasted fish food on the bottom of the tank, then you must know that soon you will have a bristle worm tank instead of a fish tank.

Good or bad worms?

Like mentioned above, Bristle worms can settle in one of the two categories: good worms and bad worms. Most of the bristle worms that are found in salt water aquariums are good worms, they help clean up the tank and maintain a good water quality.

When it comes to bad worms, all aquarists fear the Fireworms. But not all Fireworms are bad, some of them are harmless just like the good ones, but there is one species in particular that catches our attention and that is the Breaded Fireworm (Hermodice carunculate). This one loves to chew on corals and it is a nightmare to have it inside the tank.

Fireworms tend to have more pronounced bristles with a reddish color at their base. Their body also tends to be more massive compared to other species of bristle worms.

Stings, doesn’t it?

The bristles, tiny hairy spikes, that these worms come equipped with are their defence mechanism against the outside world. The bristles are quite harmless, they don’t have any toxin or venom on them, the pain comes from the trauma of having dozens of them stuck in your finger.

Many fish tend to avoid them and some that are unlucky will have their scales torn apart by those tiny spikes. That’s why when cleaning up the aquarium or handling Bristle worms it is recommended that we wear protection gloves to avoid being stung.

If the inevitable happens, there are easy methods to get around the pain. Duct tape can be used to remove the spikes from the flesh and vinegar can be poured on the area to relive the pain. Why vinegar? Vinegar is an acidic substance that will counter the effect of the calcium (a base) that coats the bristles.

Getting rid of bristle worms

There are 2 ways to get rid of bristle worms. There is the natural way in which we add natural predators into the aquarium, such as: Pseudochromidae, Gomphosus varius, Cheilinus oxycephalus, Thalassoma lutescens, Stenopus hispidus or Stenorhynchus setrcornis. They will hunt and eat any bristle worm they can find.

The other way is by using bristle worm traps. These can be purchased from aquarium stores that sell them or they can be made using some basic materials from around the house. These traps are the same as kitchen bug traps, they let the worm get in and then it can’t get out.

A simple example of a homemade bristle worm trap consists of a taking a water bottle and cutting it 1/3 from the cap hole. After that the part with the cap hole is inserted upside down in the remaining section and it is glued using some non-toxic adhesive. The trap is then inserted into the aquarium and when a worm comes inside it, it cannot get out.

In conclusion

It is worth removing the worms from your aquarium? That depends on how you see the problem. If the bristle worm population is high it recommended to do some culling to reduce it. Some worms are beneficial as they clean the aquarium, eat dead fish and left over food and they maintain a good water quality.

Some people do not stand seeing strange alien like centipedes swarming inside their aquarium and they tend to be creeped by them. But in the end, it is up to de aquarist to decide whether to remove or to keep them. We do advice on keeping small worms as they have an important role in cleaning the water and maintaining a healthy aquarium ecosystem.

But to avoid them in the first place, every natural aquarium decoration needs to be cleaned and sterilized properly so they are not introduced in the aquarium and to feed the fish the right amount of food to avoid having left over food on the bottom of the tank.

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