Should I buy it?
Assassin Snail
Anentome helena
Typical trade / ID note: Anentome helena (formerly Clea helena)
Also known as: clea helena, snail-eating snail, bumblebee snail, Snail-eating snail, Bumblebee snail
Fishori provides conservative planning guidance, not guarantees.
Based on typical aquarium care sources; details may vary between setups. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
A targeted tool, not a permanent stocking. Use for a pest snail problem, then plan what happens when the pest snails are gone.
Best for
Tanks with an active pest snail infestation where permanent snail stocking is not the goal.
Avoid if
You want to keep nerites or mystery snails long-term. Once pest snails are gone, assassins target any remaining snail species.
Top things that go wrong
- Mouth gap vs tiny tank mates. Predation risk toward smaller tank mates. The figure that matters is the adult mouth size against the adult prey length, not the juvenile sizes in the shop.
- Shrimp & snails. Will eat small pest snails on sight; threatens shrimplets, small nerites, and small mystery snails. Not compatible with a working invert clean-up crew.
Common mistakeAdding assassin snails to a tank with nerites. Once the bladder snails are cleared, the assassins switch to the valued snails.
What most shops don't tell you
- 1.Will pick off shrimplets and small nerite snails once pest snails run low. Plan the colony order before buying.
- 2.Bought as a generic snail clear-out and left in after the job is done. With no pest snails left, an assassin will turn on shrimplets, nerites, and small mysteries.
- 3.Added to a shrimp colony to clean up dead shrimp. The assassin learns shrimp are food and the colony stops growing.
- 4.Bought as pest snail control for ramshorn or MTS infestations. They work. A pair in a 60L can take a heavy pond-snail problem down to zero in a month. The catch is once the pest snails run out, an assassin will go for shrimplets, leftover food, or starve.
About this species
Assassin snails are small predatory snails from Southeast Asia. They bury in sand during the day and hunt other snails at night, killing small pest snails first. Despite the carnivore tag, they ignore fish entirely and only sometimes harass adult shrimp.
- Amano Shrimp40L min · same group, comparable tank size
- Blue Dream Shrimp20L min · same group, comparable tank size
- Cherry Shrimp20L min · same group, comparable tank size
- Ghost Shrimp40L min · same group, comparable tank size
- Malaysian Trumpet Snail20L min · same group, comparable tank size
- Mystery Snail40L min · same group, comparable tank size
- Nerite Snail20L min · same group, comparable tank size
- Bamboo Shrimp80L min · same fish family
- Amano Shrimpalso beginner peaceful, similar tank size
- Beckford Pencilfishalso beginner peaceful, similar tank size
- Black Neon Tetraalso beginner peaceful, similar tank size
- Bloodfin tetraalso beginner peaceful, similar tank size
- Blue Dream Shrimpalso beginner peaceful, similar tank size
- Cherry Barbalso beginner peaceful, similar tank size
No reverse lookups on file yet.
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease78
- Peacefulness58
- Community fit30
- Small-tank fit100
- Hardiness76
- Energy24
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Rough 90L+ layout: one calm centrepiece, 8–12 small tetras/rasboras, 6–8 corydoras-type bottom fish — verify every name in the pair checker before buying.
Safe directions on file include: Neon Tetra, Harlequin Rasbora, Cherry Barb.
Tank mate intelligence
Use the "Often compatible" lists as a shortlist, not a stocking plan. Always run the pair tool and check the footprint of your actual tank first. Verify behaviour for Assassin Snail against your own reading before you buy.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Assassin Snail + Neon Tetra
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
Assassin Snail is peaceful in mixed company. Treats any fish small enough to fit in its mouth as food. Mouth size at adult length matters, not the prey's listed adult size.
Stress / aggression triggers on file
- Sudden crowding
- Poor water quality
Fin nipping: Not a habitual fin-nipper, but individuals can still test fins under stress or in a crowded tank.
Predation: Predation risk toward smaller tank mates. The figure that matters is the adult mouth size against the adult prey length, not the juvenile sizes in the shop.
Territory: Not strongly territorial, but still claims a working area in the tank. Give it room to settle without overlapping the next species' patch.
Planted tanks: good — easy plant ideas
In the glass: typical and warning signs
- Often calm on the glass — bursts of movement around food or tank disturbance.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Low listed risk — still watch new introductions.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
medium-hard
Diet
carnivore
Small invertebrates, frozen bloodworm or daphnia, and protein-rich prepared foods. Rotate the menu and feed by appetite rather than by clock.
Shrimp & snails
Will eat small pest snails on sight; threatens shrimplets, small nerites, and small mystery snails. Not compatible with a working invert clean-up crew.
Two or three for active pest control in a 60L. More than that in a small tank wipes the food supply and the assassins starve.
Breeding behaviour depends on the species. Research before you buy a mixed-sex group of this fish.
- An exit plan. Once pest snails run out, the assassins need re-homing, supplementary feeding, or a tank without small shrimp.
- Sand substrate. Assassins bury during the day. A bare or gravel tank stresses them.
- Confirmation that you do not also want to keep nerites, small mysteries, or a breeding shrimp colony long-term.
- Tank volume meets or exceeds 30L published minimum for adults.
- Heater can hold 20–28°C without cooking cooler-water tank mates.
- No tank mates small enough to fit the adult mouth gap for this species.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 30L minimum tank needs a filter rated for at least 120L/hr turnover and a heater to hold 20–28°C reliably.
Plant suggestions
Assassin Snail does well in planted tanks. Plants compatible with 20–28°C and pH 7–8:
Profile status: partially verified · Evidence tier: medium · 2 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Anentome helena
Primary: species page covering range, predatory feeding, and breeding behaviour (lays single eggs, slow reproduction).
- Aquarium Co-Op. Assassin Snails for Pest Snail Control
Secondary: retailer guide on stocking density for pest control, target snail species, and shrimp-safety caveats.
Evidence notes
- Assassin snails do not breed in plague numbers. They lay single eggs on hard surfaces and reach adult size in six months or so, which keeps the population from collapsing the food supply.
- Shrimp safety is conditional. Adult Amano and cherry shrimp are usually ignored, but moulting shrimp and shrimplets are vulnerable in tanks where pest snails have run out.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.