Are Bristle Worms Good or Bad For Aquariums?

Let’s be honest - except perhaps a predator, few things can make a reef hobbyist cringe more than catching a glimpse of a bristly, segmented creature slithering across the aquarium glass during a late-night tank check (it's not exactly the aquarium gift that many hobbyists desire). That distinctive wriggling motion will send many of us running to find the tweezers or traps. Now wait a minute, are these pricky hitchers really villains, or are they allies that we just don’t understand in our reef ecosystems?

What are bristle worms?

Bristle worms are members of the class Polychaeta, a group of segmented worms that comprises more than 10,000 species. Their most distinguishing trait is the hair-like bristles (known as chaetae) that extend from each segment of the body. These hairlike bristles do more than give it a hairy appearance; they help it move and act as protection.

Most bristle worms found in home aquariums are:

• Normally 1-6 inches in length (some are much bigger)

• Divided by clearly seen bristles protruding from every section

• Capable of stretching and contracting to squeeze into tiny places

• Usually tan, pinkish-brown, or grayish (beneficial Species)

• Most active during the night (they are nocturnal animals)

The Great Debate - Bristle worms Friend or Foe?

The Positive Aspect of Bristle Worms

• Most bristle worms found in home aquariums are detritivores that eat dead organic material, leftover food, and fish waste. Consider them the vacuum cleaners of your aquarium ecosystem.

• Bristle worms have the added benefit of aerating their environments.

• They do their work, often at night, without you watching, and they help keep the tank a bit cleaner, requiring no care from you.

• Their ability to break down organic materials assists in breaking down waste into usable forms for helpful bacteria, thus, closing the nutrient cycle in your closed ecosystem.

The Troublesome Side of Bristle Worms

• The bristles can break off and lodge into your skin like tiny fiberglass splinters, causing irritation and pain. Anyone who’s been “stung” will tell you it’s not something you want to experience in a new outfit.

• A sudden bloom of bristle worms usually suggests overfeeding or poor upkeep skills. When you begin to notice that there are worms everywhere, something is likely out of balance.

• Let’s face it—many hobbyists just don’t find these creatures attractive. A worm-swarming tank during evening feed time is not precisely the picturesque reef scene most of us want.

Bristle Worms To Watch Out For

Not all bristle worms are beneficial scavengers. Certain species, such as the notorious fireworms (Hermodice carunculata), are predatory and can threaten corals, clams, and even small fish.

How Identifying What Bristle Worm You've Got

The first step before doing anything, is to determine what kind of bristle worm has moved into your tank. The distinction between helpful scavengers and dangerous predators is a big one.

Helpful Bristle Worms (Eurythoe complanata and other similar species)

• Color: Pale pinkish-brown to grayish, occasionally with faint iridescence

• Bristles: Thin, uniformly spread, typically colorless or white

• Body Type: Comparatively lean body structure

• Behavior: Peaceful scavengers that scatter at the sight of light

• Length: Usually 2-6 inches when extended

Harmful Fireworms (Hermodice carunculata and relatives)

• Color: Generally bright red or orange body with a striking reddish hue around bristles

• Bristles: Stout & pronounced with white tips

• Dark Body: more robust and thick body

• Behavior: More aggressive and may not retreat as quickly after exposure

• Size: May live longer than 15 years and average over 12 inches

• And the infamous bobbit worm (Eunice aphroditois) - one of the truly nightmarish beasts on Earth, growing to several feet long and known to ambush fish. Luckily, these are rare in home aquariums, but if one is spotted, it is best to remove it immediately!

Managing Bristle Worms in aquariums

If you've concluded that your bristle worm population needs to be managed (whether due to them being of a harmful variety or just too numerous), here are some effective methods:

Prevention

• Quarantine new additions before adding them to your aquarium 

• Perform regular water changes

• Follow appropriate feeding habits

• Provide adequate filtration 

Bristle Worm Removal Methods - Manual Removal

Tools needed include long tweezers, tongs, or a syringe. These are the most useful tools in removing any worms that are easily accessible. But glove up first - always use gloves! Those bristles can lead to painful irritation if they get stuck in your skin.

When removing bristle worms, move slowly, and grip tightly as bristle worms can travel surprisingly quickly when they feel threatened.

Traps to catch bristle worms

Step 1: Select your type of trap. There are two types of traps you can choose: 

1. Commercial traps

2. DIY trap - use a small container and a normal funnel upside down as an entrance, with shrimp or fish food as bait

Step 2: Place traps where worms are active. This is typically usually near the substrate or rock crevices. After placing traps, check them daily; after worms have been active overnight, is the best time, ideally in the morning.

Natural Predators

You can also introduce some fish or invertebrates that eat bristle worms for population control:

• Arrow Crabs

• Wrasses

• Dottybacks

• Hawkfish

Important: Consider compatibility when introducing predators to your self-contained environment. Some predatory species of bristle worms may also harass other, more desirable critters in your tank.

So You’ve Been Stung: Bristle Worm First Aid

If you have the unfortunate experience of getting bristle worm bristles stuck in your skin, here’s how to treat it:

Remove Visible Bristles:

• You can try using adhesive tape pressed onto the area then remove it carefully 

• Apply a thin layer of white school glue, wait for it to dry, then carefully peel it off

• For bigger bristles, tweezers may do the trick

Hot Water Treatment:

• Immerse the affected area in hot (but not scalding) water for 20-30 minutes

• Target water temp between 110-113°F (43-45°C)

• The heat serves to denature the protein-based toxins within the bristles

After-Care:

• Use a topical antihistamine or hydrocortisone cream to reduce swelling and itching

• Take an oral antihistamine if the reaction is more widespread

• Keep an eye out for infection or a severe allergic reaction

Conclusion

Bristle worms, like many things in the reef aquarium hobby, are a reflection of the balance that has been cultivated within natural ecosystems. A few types of bristle worms can be problematic, but the majority of the bristle worms found in home aquariums are beneficial scavengers that are key to a healthy reef ecosystem.

If you are unsure whether the bristle worm you have in your aquarium is good or bad, or would like further tips to help remove bristle worms from aquariums, feel free to contact the Reefco Aquariums Team today.