Assassin Snail (Clea helena) is the most effective biological solution to pest snail problems in the freshwater aquarium hobby — a striking, conical-shelled carnivore that hunts and consumes bladder snails, pond snails, ramshorn snails, Malaysian trumpet snails, and other unwanted snail species with quiet efficiency. The shell displays alternating yellow and dark brown-black spiral banding that is immediately eye-catching — the Assassin Snail is as attractive as it is useful.
Native across Southeast Asia — Thailand, Malaysia, Indonesia, Cambodia, Vietnam, and Laos — where it inhabits streams, rivers, canals, and ponds with soft substrate. Clea helena is one of a very small number of whelk species (traditionally marine snails) that has fully adapted to freshwater life — a remarkable evolutionary story. Assassin Snails require both male and female to breed and cannot self-fertilize, meaning population growth is slow and manageable — a stark contrast to the pest snails they control.
Assassin Snails are primarily snail hunters but will also consume worms, carrion, and protein-based sinking foods when snail populations are low. They partially bury themselves in the substrate while hunting, which also gently aerates the tank bed. While Assassin Snails are focused snail hunters, they may occasionally investigate very small baby shrimp — in heavily stocked shrimp breeding tanks this is worth considering, though it appears to be relatively uncommon behavior and adult shrimp are generally left alone.
| Assassin Snail | |
|---|---|
| Difficulty | Beginner — Easy |
| Adult Size | Up to 1.25 inches (3 cm) |
| Recommended Stocking | 1 per 5 gallons for pest control; 3–4 in 20+ gallons to ensure breeding pair |
| Ideal Temperature | 75–82°F (24–28°C) |
| Ideal pH | 7.0–8.0 |
| Ideal GH | 8–15 dGH |
| Ideal KH | 3–10 dKH |
| Staple Food | Live pest snails (primary); Hikari Sinking Wafers (supplement) |
| Treat / Supplement | Glasgarten Mineral Junkie Treats; Glasgarten Mineral Treats |
| Origin | Southeast Asia — Thailand, Malaysia, Indonesia, Cambodia, Vietnam, Laos |
| Notes |
Pest Control: Hunts and consumes bladder, pond, ramshorn, and MTS snails Breeding: Requires both sexes — slow, manageable population growth Substrate: Soft substrate preferred — partially buries while hunting Shrimp: Generally safe with adult shrimp; caution with very small baby shrimp Copper: Fatal |
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