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Assassin Snail
Clea helena
Animalia›Mollusca›Gastropoda›Nassariidae
📍 Southeast Asia
Assassin snails are the go-to solution for controlling pest snail infestations in freshwater aquariums. They hunt and consume other snails methodically, and will also scavenge meaty foods. They breed slowly and do not typically overrun a tank like pest species do.
Care Guide
Diet
Assassin snails are carnivorous and primarily hunt smaller snails, making them excellent for pest control. Supplement their diet with sinking protein pellets and frozen bloodworms 2-3 times weekly. They will also scavenge dead fish and organic debris, but should not rely solely on this for nutrition.
Behavior
Assassin snails are methodical hunters that actively search for and consume pest snails, though they remain peaceful toward fish and shrimp. They are primarily nocturnal and spend daylight hours buried in substrate or hiding among plants. They move slowly but deliberately, and a single snail can significantly reduce pest snail populations over time.
Breeding
Breeding in captivity is slow and infrequent, making assassin snails unlikely to overpopulate an aquarium. Females lay small individual eggs on hard surfaces like rocks and driftwood, which hatch after several weeks. Breeding is difficult to trigger intentionally and rarely occurs unless conditions are optimal.
Tank Mates
Peaceful shrimp that occupy different ecological niches; assassin snails may occasionally prey on shrimplets but generally coexist well
Larger shrimp species that are less vulnerable; compatible water parameters and peaceful temperament
Small peaceful fish that occupy mid-water column; no predation risk and compatible temperature/pH ranges
Peaceful, slow-moving fish that won't compete for food; similar water temperature preferences
Peaceful algae-eaters with identical water requirements; both are small and non-aggressive
Common Diseases
Shell Erosion
Pitting, holes, or thinning of the shell; discoloration or chalky appearance
Increase water hardness (5-20 dGH) with calcium supplements or crushed coral; ensure pH remains stable at 7.0-8.0; provide cuttlebone or calcium-rich foods
Parasitic Infection
Lethargy, reduced feeding, visible parasites on body or shell, mucus buildup
Perform 25% water changes and improve water quality; quarantine if possible; avoid copper-based treatments which are toxic to snails
Bacterial Infection
Shell decay, foul odor from shell, tissue damage, inability to retract into shell
Improve water quality with frequent partial water changes; maintain optimal temperature (20-27°C); remove decaying food promptly; ensure adequate calcium for shell repair
Starvation
Inactivity, weight loss, failure to hunt or feed, shell becomes thin and brittle
Ensure regular feeding of protein-rich foods (bloodworms, sinking pellets); provide adequate pest snails or supplement diet; verify snail is not being outcompeted for food
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Quick Facts
- diet
- Carnivore/Scavenger – pest snails, bloodworms, sinking protein pellets
- breeding
- Slow; lays small individual eggs on hard surfaces
- lifespan
- 2–3 years
- max size
- 3 cm (1.2 in)
- tank size
- 10 gallons minimum
- temperament
- Predatory toward snails; peaceful toward fish and shrimp
Water it likes
- ph
- 7.0–8.0
- ammonia
- 0 ppm
- nitrate
- <20 ppm
- hardness
- 5–20 dGH
- temperature
- 68–81°F (20–27°C)