By Connor Boyle
The chemical-free fix for a pest-snail outbreak
If your tank has been taken over by bladder snails or Malaysian trumpet snails — the tiny hitchhikers that arrive on plants and multiply overnight — the assassin snail (Anentome helena) is the calm, natural answer. It's a small predatory snail that does exactly one thing brilliantly: it hunts and eats other snails. No snail-killing chemicals (which quietly poison shrimp and other invertebrates), no tearing the tank down — just a few assassins quietly bringing the population back under control over a few weeks.
What makes them ideal is the balance: they're effective enough to clear an outbreak, but they breed so slowly that they never become a pest themselves. They're peaceful with fish and adult shrimp, easy to keep, and genuinely interesting to watch as they burrow through the substrate and emerge to hunt.
Care at a glance
Assassin snails are hardy and beginner-friendly, with one thing worth getting right: water hardness. Their conical, gold-and-brown banded shells are built from calcium, and in soft, acidic water those shells slowly pit and erode. Aim for neutral-to-alkaline water (pH 7.0–8.0) with moderate-to-hard mineral content. If your water is naturally soft, a cuttlebone or a small amount of crushed coral keeps their shells solid.
Give them sand or fine, smooth gravel — they burrow to ambush prey and to rest. A standard tropical temperature of 21–27 °C suits them, and a 40 litre tank is plenty for a small working group. Avoid copper-based medications and fertilisers, which are toxic to all snails and shrimp.
What they eat (and what they leave alone)
Their staple is other snails — bladder, ramshorn and trumpet snails are all on the menu. They will not harm your fish, and they generally leave large healthy ornamental snails (like adult Nerites and Mystery snails) alone, although very small or weak ones can be at risk.
Once the pest snails run low, don't let your assassins go hungry: drop in sinking carnivore pellets, frozen or freeze-dried bloodworms, or a sinking shrimp wafer a couple of times a week. They won't touch live plants or eat algae — they're pure carnivores.
Tank mates
Peaceful community fish, Corydoras, tetras, rasboras, and shrimp all make good companions. Assassins are far too slow to threaten anything that can swim. They're a natural fit alongside a cherry shrimp or amano shrimp clean-up crew, and pair well with a planted, nature-style tank.
Buying assassin snails in the UK
We hand-select healthy, active assassin snails and ship them with a live arrival guarantee and tracked UK delivery. For a typical outbreak, start with roughly one snail per 8–10 litres — a small group also lets them breed slowly and keep your tank pest-free for the long term.
Browse our live assassin snails below, or explore the rest of our aquarium snails and clean-up crew.
