Guide
Assassin snails: the James Bond of snails — license to kill
They don’t graze algae. They don’t tidy detritus. They hunt other snails. Meet the assassin snail: the hitman of the freshwater tank.
What is an assassin snail?
Clea helena (formerly Anentome helena) is a small, cone-shaped snail with a striped yellow and brown shell. It’s a carnivore. While most aquarium snails are scavengers or algae eaters, the assassin has one job: find other snails, drill into them, and eat them. No licence required from you — just a tank and a snail problem (or a willingness to feed them).
License to kill: how they hunt
Assassins track prey by scent, burrow into the substrate to ambush, and use a radula and proboscis to bore into the shell of the victim and consume the soft body. They take down bladder snails, ramshorns, Malaysian trumpet snails, and even small mystery snails. They work slowly but steadily; a few assassins can make a real dent in a pest snail population over weeks or months. They’re not a magic overnight fix — but they’re effective, chemical-free, and fascinating to watch.
Care and tank mates
Assassins are easy to keep: normal tropical temps (mid-70s °F), stable water, and either pest snails to eat or supplemental food (sinking pellets, frozen meaty foods). They breed slowly (they lay single eggs, not clutches), so you won’t be overrun. Keep them away from snails you want to keep (e.g. prized nerites or mystery snails) — they don’t distinguish between pest and pet. They leave fish, shrimp, and plants alone; fish and shrimp are safe. Some keepers report assassins taking very weak or dying shrimp; healthy shrimp are usually fine.
When to use them
Ideal when you have a pest snail explosion and don’t want to dose chemicals (which can harm shrimp and sensitive fish). Add a few assassins, let them do their job, and either leave them as part of the crew or rehome them once numbers are down. If you have no snails left, they’ll need sinking food. Track your tank inhabitants (e.g. in App-aquatic) so you know what’s in there — and remember: with assassins, the name says it all.
Quick takeaways
- Assassin snails (Clea helena) eat other snails; they’re the hitmen of the aquarium.
- They hunt by scent, burrow, and drill into prey; effective against bladder, ramshorn, MTS, and similar.
- Don’t mix with snails you want to keep; safe with fish and shrimp. Easy to care for; supplement food if pest snails run out.