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Aquarist First Aid – Bristleworm Spines

BristlewormAlmost every saltwater aquarium that has had live rock or corals has bristleworms. They may not be obvious, you may not see them, but chances are that they are there…and their “attacks” are some of the most common injuries that hobbyists encounter.

What they are

Bristleworms are polychaete worms related to the earthworms in our gardens on lands and the ornamental feather duster worms kept in aquariums. They are nocturnal and live buried in the sediment or crawling deep within rockwork. They feed off of leftover food and detritus in the aquarium and in aquariums with lots of food for them can multiply to epidemic proportions. Each worm can be anywhere from microscopic in size to up to two feet or more in length. In aquariums, most aquarists usually start seeing them (and getting concerned) when they are just a few inches in length.

Most bristleworms are not inherently bad. The major problems with them (other than the EWW-factor) comes with the bristles from which they get their name. These bristles are made from chitin – the same material that forms the exoskeleton of most insects and crustaceans – and they are super thin and razor sharp. Touching the bristleworm itself (not recommended!) will drive the spines into a hand where they can break off, but direct contact isn’t always necessary. Spines can be left on rocks, in the substrate, in or on nets and other equipment, even in the water itself. Most of the time, an aquarists won’t even realize they are stung until the spines gets moved or brushed. The spines themselves are usually fairly transparent and can be very short.

What to do

Symptoms of being stung can be a rash or a needle-like prick or irritation. The worms known as Fireworms can have a powerful venom in their hollow spines that can cause burning, itching, a painful rash and occasionally more serious symptoms in dangerous worms or sensitive “victims”. Once you identify where the pain is coming from, look for the spines. A magnifying glass and good lighting can help you find them. You can use a pair of tweezers to remove any spines you can find. If you can find tweezers with a magnifying glass built onto them, that would be an excellent addition to your Aquarist First Aid Kit; we have one here that is invaluable!

Once you’ve gotten all the spines you can see, you can try to remove any you can’t. Tape works – medical or otherwise – and we’ve even found that sticky lint rollers work really well. When you believe all the spines have been removed, clean the area with an antiseptic like rubbing alcohol or peroxide so the punctures don’t get infected or irritated. The spines aren’t easily dissolved or neutralized like anemone stings but luckily, they don’t usually go deep so any that are left usually get “shed” as your skin cells shed away. If the sting was from a fireworm, a topical hydrocortizone ointment can help get rid of any rash that may develop.

If you experience shortness of breath, dizziness, nausea, muscle soreness or any other such symptoms, seek medical attention! This basic treatment and advice is no substitute for professional medical care. Though stings from fireworms are not usually serious, some individuals are more sensitive than others and these symptoms can indicate a severe reaction to the neurotoxin.


FirewormIn some ways, “prevention” isn’t necessarily possible. “Preparedness” may be a better term here. Chances are, if you make contact with a bristleworm once in your aquarium, it’ll probably happen again. If you are working in the substrate or with the rockwork in your aquarium, wear gloves to help protect your hands from direct contact. Spying on your aquarium at night (after the lights have been off or early before they come on) can help you spot them. Avoid overfeeding your aquarium can help keep populations under control (and it will help your water quality too).

And if you are reading this blog because you’ve just got your first bristleworm spine in your finger? Consider it an initiation into the hobby!

Thanks, Eileen


  1. avatar

    Wow. Reason #362 to stay with freshwater. 🙂


  2. avatar

    Has anyone had any longer term effect from being stung I had many ofthese in my tank and was stung quite badly it stung amost unbearable pain and for weeks after the pain kept flaring up over and over I also felt quite sck and i still don’t know if a coincidence or not but have had headaches, and muscle pain since??

  3. avatar

    Hello Michelle, For any situation like this, seek professional medical attention. Symptoms like that may be unrelated, but they may also be from the more dangerous and venomous Fireworms. Some Fireworms have a neurotoxin that can cause irritation, sore muscles and other symptoms, especially if someone is more vulnerable to similar neurotoxins like bee or wasp stings. The bristleworms most commonly found in aquariums can have painful spines but don’t usually cause lasting effects unless you are particularly allergic to them. I would contact your doctor if you are still experiencing symptoms or consult a doctor familiar with marine animal stings; a local SCUBA or dive shop may be able to refer you to someone in your area.

  4. avatar

    really pleasant

About Eileen Daub

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Marine Biologist/Aquatic Husbandry Manager I was one of those kids who said "I want to be a marine biologist when I grow up!"....except then I actually became one. After a brief time at the United States Coast Guard Academy, I graduated from Coastal Carolina University in Myrtle Beach, South Carolina in 2004. Since then, I've been a marine biologist at That Fish Place - That Pet Place, along with a Fish Room supervisor, copywriter, livestock inventory controller, livestock mail-order supervisor and other duties here and there. I also spent eight seasons as a professional actress with the Pennsylvania Renaissance Faire and in other local roles. If that isn't bad enough, I'm a proud Crazy Hockey Fan (go Flyers and go Hershey Bears!).