Assassin Snail
Anentome helena
A highly effective and popular carnivorous freshwater snail used primarily for pest snail control. They actively hunt and consume smaller snails like bladder, ramshorn, and pond snails. Featuring a striking yellow and dark brown spiraled shell, they are a functional and attractive addition to aquariums. Unlike many aquatic snails, they are not hermaphroditic and reproduce quite slowly.
Assassin Snail At a Glance
Assassin Snail Tank Requirements
Will Assassin Snail fit in your tank?
Care guides tell you what Assassin Snail needs, the next question is whether your tank can safely provide it. Test Assassin Snail against your tank size, maintenance needs, and the fish you already keep before you buy.
Assassin Snail Water Parameters
Assassin Snail Temperament & Compatibility
Assassin Snail Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard
The standard Assassin Snail form found in the aquarium trade. They spend much of their time buried in sandy substrates, waiting to ambush passing pest snails.
Same care requirements as the base species
Also known as: Common Assassin Snail
Assassin Snail Care Guide Summary
The Assassin Snail, scientifically known as Anentome helena, belongs to the Invertebrates family group. Adults reach a maximum size of approximately 2.5 cm and have a globular body shape with a slow growth rate. Classified as peaceful, this species primarily occupies the bottom zone of the aquarium and produces a low level of biological waste.
To thrive, the Assassin Snail requires a freshwater only aquarium with a minimum volume of 10 litres and a tank length of at least 20 cm. Water temperature should be maintained between 22°C and 28°C, with a pH range of 7–8 and a general hardness of 8–15 dGH. A low water flow is preferred.
The Assassin Snail is a rewarding species to keep, provided its core environmental needs are met. The Assassin Snail is typically available in one standard form.
Assassin Snail Habitat Setup
When setting up an aquarium for the Assassin Snail, a low water flow best suits their natural preferences. Because this species occupies the bottom zone, the aquarium layout should prioritise sufficient floor space with hiding spots among rocks, wood, or dense planting. Useful additions include a sand substrate to accommodate their sifting behaviour. Keepers should note that expect substrate disturbance, so lightweight décor should be secured.
Assassin Snail Compatibility Notes
Classified as peaceful, the Assassin Snail is adaptable and can be kept singly or in a small group, offering flexibility when planning a community tank. When choosing tankmates, snails will be treated as food rather than tankmates. Selecting tankmates that favour different water layers from the bottom zone can help reduce competition and territorial overlap.
Who Assassin Snail Is Actually For
Assassin Snail is best for a fishkeeper who wants a species that can settle into a calmer community setup and can provide someone who understands its individual space requirements. It makes the most sense for a hobbyist who will actually build around its needs, especially sand.
The most common mistake is treating Assassin Snail like any other community fish and skipping the soft sand it needs to forage safely. Another frequent problem is forcing it into an over-busy community when it would do better with more room or more deliberate tankmate choices.
Assassin Snail Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Assassin Snail.
5 Gallon
10 Gallon Standard
15 Gallon Standard
20 Gallon High
20 Gallon Long
29 Gallon Standard
Show 27 more tank sizes
Frequently Asked Questions About Assassin Snail
How big does Assassin Snail get?
Assassin Snail (Anentome helena) typically reaches a maximum adult size of approximately 2.5 cm. They have a globular body shape and a slow growth rate.
What tank size does Assassin Snail need?
A minimum aquarium volume of 10 litres and a tank length of at least 20 cm are recommended for Assassin Snail. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Assassin Snail need?
Assassin Snail thrives in freshwater only conditions with a temperature range of 22–28°C, a pH between 7 and 8, and a general hardness of 8–15 dGH. A low water flow is preferred.
Is Assassin Snail peaceful or aggressive?
Assassin Snail is classified as peaceful with an aggression score of 2 out of 10. They are generally well-suited to peaceful community tanks.
Can Assassin Snail live alone?
Yes, Assassin Snail can be kept singly or in a group. They are flexible and adapt well to both setups.
Will Assassin Snail eat snails?
Yes. Assassin Snail actively feeds on snails. While this can be useful for controlling pest snail populations, it means decorative snails should not be housed with this species.
Does Assassin Snail have any special tank requirements?
Yes. Assassin Snail benefits from sand (sifters) in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Useful setup supplies
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- April 28, 2026
- Last updated
- April 28, 2026
- Issues or corrections?
- Contact the editorial team
Top Tank Mates for Assassin Snail
These fish are strong compatibility matches for Assassin Snail based on water preferences, temperament, adult size, and tank behavior.
Kabia rainbowfish
Glossolepis kabia
Ideal Tank MatesScissortail Rasbora
Rasbora trilineata
Ideal Tank MatesRummynose Rasbora
Sawbwa resplendens
Ideal Tank MatesRosy Red Minnow / Fathead Minnow
Pimephales promelas
Ideal Tank MatesRose Danio
Danio roseus
Ideal Tank MatesRed Dwarf Rasbora
Microrasbora rubescens
Ideal Tank MatesPlants That Suit Assassin Snail
These plants pair well with Assassin Snail based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Amazon Frogbit
Limnobium laevigatum
Asian Watergrass
Hygroryza aristata
Asian Watermoss
Salvinia cucullata
Carolina Mosquito Fern
Azolla caroliniana
Common Duckweed
Lemna minor
Crystalwort
Riccia fluitans
Fish Similar to Assassin Snail
Bladder Snail (Pest Snail)
Physella acuta
A tiny, fast-moving freshwater snail almost universally introduced accidentally via live aquarium plants. While frequently labeled a 'pest' due to their rapid, prolific reproduction, they are actually an excellent cleanup crew. They consume algae, uneaten food, and decaying plant matter without harming healthy plants. They are hermaphroditic and can self-fertilize, meaning a single snail can start a massive colony.
Mystery Snail
Pomacea bridgesii
A large, popular, and active freshwater snail. Unlike other apple snails, they generally do not eat live, healthy plants, preferring algae, detritus, and sinking foods. They require calcium-rich, alkaline water to prevent shell erosion. Females will frequently leave the water to lay distinct pink egg clutches above the waterline.
Trapdoor Snail
Cipangopaludina chinensis
A large, livebearing freshwater snail named for its tough operculum (trapdoor) used for defense against predators and harsh conditions. They are excellent scavengers and algae eaters, heavily favored for outdoor ponds and unheated aquariums due to their extreme cold tolerance. They require hard, alkaline water to prevent shell erosion.
Horned Nerite Snail
Clithon corona
A highly effective and tiny algae-eating snail characterized by the horn-like spikes on its shell. It is completely peaceful and will not reproduce in freshwater (though it may lay unsightly white eggs on decor). It requires an established tank with plenty of algae and hard, alkaline water to prevent shell erosion. Known to climb out of aquariums if a lid is not secure.
Olive Nerite Snail
Neritina reclivata
The Olive Nerite Snail is highly prized for its exceptional algae-eating abilities and completely peaceful nature. They have a rounded, smooth, olive-green shell. Unlike many freshwater snails, they will not overpopulate an aquarium because their eggs require brackish or saltwater to hatch and develop. They are notorious escape artists and will climb out of the water, so a tight-fitting lid is mandatory.
Nerite Snail
Neritina natalensis
The gold standard for algae control in freshwater aquariums. Native to Africa, these snails are renowned for their voracious appetite for diatoms and spot algae. A key feature is their inability to breed in freshwater; they lay white sesame-seed-like eggs that will not hatch without brackish/marine conditions, preventing population explosions. They are escapists and require a tight-fitting lid.