Bobbit worm (Eunice aphroditois) care guide

Group
Other invertebrates
Other names
Sand striker, Trap-jaw worm, Bobbitt worm
Family
Eunicidae
Origin
Warm seas of the Atlantic and Indo-Pacific; sand, mud and around rocks, sponges and coral reefs to 95 m
Water
saltwater
Maximum size
300 cm
Temperament
aggressive
Reef safe
no
Lifespan
3–5 years

Care

The bobbit worm is a large predatory bristle worm that buries itself in sand or rock and ambushes passing animals. It is a pest in reef aquariums and should not be sold as livestock. Its body is slim, deep purple to black and iridescent, with five antennae on the head and powerful hooked jaws. Wild worms range from under 10 cm to almost 3 m, and the longest recorded was 299 cm, making it the longest known polychaete. How it arrives: small specimens hide in live rock and grow inside the aquarium, sometimes unnoticed for years. They can dig into rock and curl into small spaces, which makes them hard to find. Identification: look at night with a red torch. You may see a ring of antennae or a shiny segmented body poking from a hole in rock or sand, or the worm may lunge at food. Fish that vanish without trace, injured or half-eaten fish, and corals or clams torn at the base are warning signs. Harm: it strikes with retractable jaws that stun prey and can cut small fish in half, then drags them into its burrow. It eats fish, shrimp, snails and other invertebrates and can steadily empty a tank. Handle with care: its bite and bristles can injure skin. Wear gloves. Removal and prevention: quarantine and inspect all live rock; cured or dry rock avoids the risk. To remove a worm, use a baited worm trap at night, or take out the rock it lives in and treat it in a bucket of hypersaline (very salty) water or fresh water, which drives worms out. Cutting the worm usually fails, because it can regrow its rear end. There are no reliable natural predators in home aquariums. Copper: copper-based medicines are toxic to shrimp, snails and most invertebrates, and some plant fertilisers carry copper too. Never treat a display tank holding this animal with copper; treat fish in a separate hospital tank, and drip-acclimatise new arrivals slowly. Sources: Wikipedia (en.wikipedia.org/wiki/Euniceaphroditois). Checked October 2026.

Diet

Ambush predator: fish, shrimp, crabs, snails and other animals that pass its burrow. It should not be fed or kept.

Breeding

It reproduces sexually: adults release eggs and sperm into the water and the larvae drift as plankton before settling. There is no scientific evidence that it splits to reproduce, although it can regrow its rear segments if cut.

Compatibility and tank mates

Harmful to fish and most invertebrates. Not reef safe. Remove it from any community tank.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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