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title: "Assassin Snail: The Complete Care, Pest-Control & Breeding Guide" description: "The definitive assassin snail (Clea helena) care guide: natural pest-snail control, whether they harm shrimp or plants, hard-water needs, diet, slow breeding, and tank mates." slug: assassin-snail commonName: Assassin Snail scientificName: Clea helena family: Nassariidae order: Neogastropoda difficulty: Beginner minTankSize: 5 temperature: "72–82°F (22–28°C)" ph: "7.0–8.0" hardness: "8–18 dGH" lifespan: "2–3 years" maxSize: "1.2 inches (3 cm) shell" origin: "Southeast Asia — Thailand, Malaysia, Indonesia" publishedAt: "2026-06-04"

Assassin Snail: The Complete Care, Pest-Control & Breeding Guide

The assassin snail is the hobby's most elegant solution to a pest-snail outbreak — a handsome, conical, gold-and-brown-striped snail that hunts and eats other snails, providing natural biological control without chemicals or fish. Clea helena delivers on its dramatic name (it really does hunt down bladder, ramshorn, and trumpet snails) while remaining peaceful toward fish, generally safe with adult shrimp, and completely plant-safe. Best of all, it breeds slowly, so it never becomes a pest itself.

This guide is the complete reference: the assassin snail's biology and hunting, how to use it for pest control, whether it threatens shrimp or plants, its hard-water and diet needs, its slow breeding, and which tank mates suit it.

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Species Overview

The assassin snail (Clea helena, sometimes Anentome helena) is a carnivorous freshwater snail from Southeast Asia, reaching about 3 cm (1.2 inches). It's genuinely attractive — a glossy, conical (cone-shaped) shell banded in alternating gold/yellow and dark brown stripes — making it a display animal in its own right, not just a utility snail. Unlike the algae-and-detritus-grazing snails, the assassin is a predator and scavenger that hunts other snails and eats carrion and protein.

The assassin snail is the premier natural pest-snail control: it hunts and consumes pest snails (bladder, ramshorn, trumpet), making it the go-to biological solution for a snail outbreak. It's peaceful toward fish, plant-safe, and generally safe with adult shrimp (it can't catch healthy ones, though it may scavenge weak, sick, or freshly-moulted shrimp or pick off shrimplets). Crucially, it breeds slowly, so unlike the snails it eats, it never overpopulates. It needs hard water and calcium for its shell and a sand substrate to burrow in. It lives 2–3 years.

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Natural History and Origin

Clea helena is native to the slow, soft-substrate freshwaters of Southeast Asia — Thailand, Malaysia, Indonesia — where it lives on sandy and muddy bottoms, burrowing and hunting other snails and scavenging carrion. Unlike the grazing snails, it's a member of a largely predatory snail family (Nassariidae), equipped with a long extendable proboscis it uses to reach into other snails' shells and consume the soft body.

In the wild and the aquarium, the assassin snail ambushes and hunts other snails, often burrowing in sand and emerging to attack prey, using its proboscis to extract the victim from its shell. It also scavenges dead animals and protein. This carnivorous lifestyle is the basis of its hobby value (pest-snail control) and its diet needs (protein, not algae). It reproduces slowly with separate sexes, laying single eggs — the opposite of the prolific pest snails — which is why it controls them without becoming a problem itself.

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Water Parameters — Hard and Alkaline

Like all snails, assassins need hard, alkaline, calcium-rich water to maintain their shells — soft or acidic water causes pitting and erosion. Provide hard water with good KH and a calcium source (cuttlebone, crushed coral) if your water is soft. Confirm cycling with the nitrogen cycle tracker, and use the GH/KH converter and water parameters reference to maintain hard, alkaline conditions. Avoid copper, which is toxic to all snails.

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Tank Setup Guide

Tank size

A few assassin snails are happy in a tank as small as 5 gallons (19 litres), scaling to any size. For pest control, a common guideline is a few assassins per 10 gallons, adjusted to the size of the snail outbreak — more assassins clear pests faster.

Substrate — sand to burrow

Provide a sand or fine-gravel substrate — assassin snails like to burrow, ambushing prey and resting in the sand, and they're more at home and effective with a soft substrate than on bare glass or coarse gravel. Add normal décor and a calcium source for shell health.

Filtration, flow, lighting

Any gentle filtration works; assassins tolerate normal community conditions. Lighting is flexible. The key environmental needs are hard water, a sand bed, and (for their food) a supply of pest snails or protein.

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Feeding Guide — A Carnivore

Assassin snails are carnivores and scavengers, not grazers — they need protein, and they will not survive on algae.

What to feed

• Pest snails — their primary natural food; they hunt bladder, ramshorn, and trumpet snails. A snail outbreak is, for an assassin, a buffet.
• Protein foods once snails run low — frozen bloodworm, blackworms, sinking carnivore/shrimp pellets, and other meaty foods are essential once the pest population is cleared, or assassins will starve.
• Carrion — they scavenge dead fish/snails, part of their cleanup role.

How often

While clearing a snail outbreak, assassins feed on the pests. Once the pest snails are gone, you must feed them protein (bloodworm, pellets, blackworms) every couple of days, or they'll starve — a common oversight after they've done their job. They don't eat algae or plants. A healthy assassin is active, burrowing and hunting, with an intact striped shell.

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Using Assassin Snails for Pest Control

The assassin snail's main job is biological pest-snail control, and it does it elegantly:

• Add a few assassins to a tank with a bladder, ramshorn, or trumpet snail outbreak; they'll hunt the pests over days and weeks.
• They work gradually, not overnight — pest control by assassins is a steady decline, not an instant fix. For large outbreaks, combine with reducing feeding (which is what fuels the pests) and manual removal/bait-trapping.
• They won't eradicate every snail instantly, and once pests are scarce, the assassins switch to scavenging and need supplemental protein.
• Advantages over chemicals: no toxic snail-killers fouling the tank with mass die-offs, no harm to fish or plants, and a handsome display snail as a bonus.

The complete approach to a snail outbreak is: add assassins + cut feeding + vacuum detritus/bait-trap — addressing both the predators and the overfeeding that caused the bloom.

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Behavior and Temperament

Assassin snails are peaceful toward fish and (mostly) shrimp, but predatory toward other snails — they burrow in the sand, emerge to hunt, and use their proboscis to consume snail prey. Despite the dramatic name, they're slow, deliberate, and no threat to anything that isn't a snail (or a weak/moulting shrimp or shrimplet). They're handsome and interesting to watch, especially when hunting, and they double as scavengers cleaning up carrion.

Toward fish they're entirely peaceful (and being snails, fish largely ignore them, though snail-eating fish like puffers and loaches will attack assassins too — see Compatibility). Toward plants they're completely safe. Their slow, predatory, burrowing behaviour and gradual breeding make them a controlled, effective, low-risk addition — a rare "pest control" that's itself attractive and well-behaved.

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Compatibility

Assassin snails are peaceful with fish and plants, predatory toward other snails, and mostly safe with adult shrimp.

Good tank mates: peaceful community fish (tetras, rasboras, guppies, corydoras, betta), and adult dwarf shrimp in a non-breeding context (assassins can't catch healthy adult shrimp).

Cautions:

• Ornamental snails you want to keep — assassins will eventually hunt and eat mystery, nerite, and other snails too, not just pests; don't mix them with snails you value.
• Shrimp-breeding tanks — assassins may pick off shrimplets and scavenge weak/moulting shrimp; keep them out of dedicated shrimp-breeding setups.
• Snail-eating fish — pea puffers and loaches will eat assassin snails too.
• Copper-based medications — toxic to snails; avoid.

Use the compatibility checker. The key rule: assassins are for tanks where you want snails gone, not tanks with ornamental snails or breeding shrimp you want to protect.

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Breeding Guide

Assassin snails breed slowly — which is exactly why they control pest snails without becoming pests themselves. Unlike the prolific, hermaphroditic pest snails, assassins have separate sexes (you need males and females, though they're hard to tell apart, so keeping a small group ensures both) and reproduce gradually.

They lay single, square-ish, translucent eggs (one at a time) on hardscape and surfaces, rather than the large egg masses of pest snails. Each egg takes several weeks to hatch, and the tiny young then burrow into the substrate for a long period before emerging as visible juveniles, so breeding is slow and easy to miss. This slow reproduction means an assassin population grows gently and never explodes. For keepers, this is ideal: you get sustainable pest control and a few baby assassins over time, but never an assassin "infestation." A sand substrate (for the burrowing young), hard water, and a steady food supply support breeding.

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Health and Disease

Assassin snails are hardy, with most problems relating to water chemistry, starvation, or predation.

Shell erosion/pitting from soft or acidic water and calcium deficiency is the main issue — provide hard, alkaline, calcium-rich water and a calcium source. Starvation is a common, avoidable problem after the assassins have cleared the pest snails — remember they're carnivores that then need protein foods (bloodworm, pellets, blackworms), not algae. Copper poisoning from medications is lethal — avoid copper. Being snails, they can also fall prey to snail-eating fish. A dead assassin (open shell, foul smell) should be removed.

Prevention: hard, alkaline, calcium-rich, cycled water; a sand substrate; a steady food supply (pest snails, then protein); peaceful, non-snail-eating tank mates; and no copper. Given those, assassin snails are robust, effective, and long-lived.

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Interesting Facts

• A snail that hunts snails. The assassin uses a long extendable proboscis to reach into other snails' shells and consume them — natural, chemical-free pest control.
• Slow to breed, so never a pest. Unlike the prolific pest snails it eats, it has separate sexes and lays single eggs, so its population grows gently.
• Handsome and useful. Its glossy gold-and-brown striped conical shell makes it a display animal as well as a utility one.
• A carnivore, not a grazer. It needs protein (snails, bloodworm, pellets) and will starve on an algae diet — the opposite of cleanup snails.
• It eats all snails. Once the pests are gone, it'll hunt ornamental snails too, so it's for snail-eradication tanks, not mixed-snail displays.

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Bringing It Together

The assassin snail is the elegant, effective, chemical-free answer to a pest-snail outbreak — a handsome striped predator that hunts down bladder, ramshorn, and trumpet snails while staying peaceful toward fish, safe with adult shrimp, and completely plant-safe, and that breeds too slowly to ever become a pest itself. Give it hard, alkaline, calcium-rich water, a sand substrate to burrow in, and remember it's a carnivore that needs protein foods (bloodworm, pellets, blackworms) once it's eaten the pest snails — pair it with cutting back feeding for complete snail control. Just don't add it to a tank with ornamental snails you want to keep or a dedicated shrimp-breeding setup. It's the best biological pest-snail control in the hobby, and an attractive animal in its own right. Plan the build with the AI Tank Blueprint generator and dial in hardness with the GH/KH converter.