Assassin snail care guide
Also called: Bumblebee snail, Clea helena
The assassin snail is a 1-inch (2.5 cm) striped snail that hunts and eats other snails. People add it to clear out pest snails, and it breeds slowly. It's safe with fish and plants, but it will also eat nerite, mystery and rabbit snails.
Assassin snails need a tank of at least 5 gallons (19 L), and water at 22–27°C (72–81°F) with a pH of 7–8. They grow to about 2.5 cm (1 in) and are peaceful.
Plan a tank with assassin snailsSee all tank mates
Assassin snail quick facts
| Scientific name | Anentome helena |
|---|---|
| Family | Nassariidae |
| Origin | Rivers and lakes of Southeast Asia, including Thailand, Malaysia and Sumatra |
| Adult size | 2.5 cm (1 in) |
| Minimum tank | 5 gallons (19 L) |
| Temperature | 22–27°C (72–81°F) |
| pH | 7–8 |
| Hardness (GH) | 8–18 dGH |
| Group size | Can live alone |
| Temperament | Peaceful |
| Swims at | Bottom |
| Diet | Carnivore |
| Care level | Easy |
| Lifespan | 2–4 years |
| Safe with plants? | Yes |
- Needs sand or smooth, fine gravel to protect its barbels and belly.
Tank setup
One or a few can live in a 5-gallon (19 L) tank or larger. Use sand or fine, smooth gravel, because they bury themselves to wait for prey and their young live hidden in the substrate. Rocks and wood give them places to climb.
How many assassin snails in a tank?
The smallest common tank that suits assassin snails is a 5 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.
| Tank | Assassin snails (alone) |
|---|---|
| 3 gallon | Too small |
| 5 gallon | Up to 45 |
| 10 gallon | Up to 91 |
| 15 gallon | Up to 137 |
| 20 gallon | Up to 183 |
| 20 gallon long | Up to 183 |
| 29 gallon | Up to 266 |
| 40 gallon | Up to 367 |
| 55 gallon | Up to 505 |
| 75 gallon | Up to 689 |
| 125 gallon | Up to 1149 |
What you need for assassin snails
Sized for a 5 gallon tank, the smallest common size that suits assassin snails. For a different tank or a mix of fish, use the stocking calculator for a list sized to your plan.
Tank and equipment
- 5 gallon aquarium (tank or kit) (opens Amazon in a new tab)Bigger tanks are more stable and easier for beginners. How to choose
- Adjustable heater, 25 W (opens Amazon in a new tab)Holds about 76 °F (24.5 °C) in a room at 68 °F (20 °C). A bigger heater can overheat a small tank if it sticks on. How to choose
- Aquarium thermometer (opens Amazon in a new tab)Check it daily: heaters can fail stuck on or off. How to choose
- Sponge filter for 10 gallons (opens Amazon in a new tab)Gentle flow, about 15–25 GPH, suits shrimp and snails, which prefer slow water. Needs a small air pump. How to choose
- About 15 lb of aquarium sand (opens Amazon in a new tab)Enough for a layer about 1.5 in (4 cm) deep. Soft sand protects the barbels of corydoras, loaches and other diggers. How to choose
- Water conditioner (dechlorinator) (opens Amazon in a new tab)Removes chlorine and chloramine from tap water. Seachem Prime is a popular, concentrated choice. How to choose
- Liquid test kit (ammonia, nitrite, nitrate, pH) (opens Amazon in a new tab)Liquid kits are more accurate than strips. The API Freshwater Master Test Kit is the common choice. How to choose
- Gravel vacuum (siphon) (opens Amazon in a new tab)Cleans the gravel and does the water change in one go. How to choose
- LED aquarium light, about 16 in long (opens Amazon in a new tab)Match the light to the tank length. Basic LEDs grow easy plants. How to choose
Food and extras for assassin snails
- Calcium-rich snail food (opens Amazon in a new tab)Snails need calcium to keep their shells healthy.
Product links go to Amazon search results. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Disclosure.
Water parameters
Keep them at 22–27 °C (72–81 °F), pH 7.0–8.0 and 8–18 dGH. Hard, alkaline water keeps their shells smooth, so add crushed coral or a mineral supplement if your water is soft. Pitted or thin shells are a sign the water is too soft or acidic. Copper medicines kill them.
Best tank mates for assassin snails
These popular species share assassin snails' water needs and temperament. See the full list of 114 good matches.
Betta fish
6.5 cm (2.6 in) · 24–28°C (75–82°F)
Cherry shrimp
3 cm (1.2 in) · 20–27°C (68–81°F)
Guppy
5 cm (2 in) · 22–27°C (72–81°F)
Dwarf gourami
7.5 cm (3 in) · 24–28°C (75–82°F)
Neon tetra
3.5 cm (1.4 in) · 21–25°C (70–77°F)
Panda corydoras
4.5 cm (1.8 in) · 21–25°C (70–77°F)
Bristlenose pleco
12 cm (4.7 in) · 22–26°C (72–79°F)
Bronze corydoras
7 cm (2.8 in) · 21–26°C (70–79°F)
Avoid keeping assassin snails with
- Nerite snail: Assassin snail eats snails, including nerite snails.
- Oscar: Oscar eats snails, including assassin snails.
- Clown loach: Clown loach eats snails, including assassin snails.
- Discus: They need different temperatures: Assassin snail 22–27°C (72–81°F), discus 28–30°C (82–86°F).
- Dojo loach: Dojo loach eats snails, including assassin snails.
- Electric yellow cichlid: Electric yellow cichlid eats snails, including assassin snails.
Feeding
They are true carnivores. Their main food is other snails, such as bladder, ramshorn and Malaysian trumpet snails, plus snail eggs and dead animals. Once the pest snails are gone, feed sinking protein foods like frozen bloodworms or carnivore pellets once or twice a week so they don't starve.
Behavior
Slow, calm and mostly active at night. They ignore fish and plants. Healthy adult shrimp are usually too quick for them, but they can catch weak, molting or baby shrimp. Several assassins working together can kill snails larger than themselves. Pufferfish and snail-eating loaches will eat them.
Breeding
They have separate sexes that look the same, so keep five or six to get a pair. Females lay single eggs in small, clear, square capsules on hard surfaces. The eggs take about one to two months to hatch, depending on warmth. The young bury in the substrate for several months before you see them.
Tips from experienced keepers
- Don't add them to a tank with nerite, mystery or rabbit snails you want to keep.
- Use sand or fine gravel. Babies stay buried for months and need a soft substrate to survive.
- Feed bloodworms or sinking pellets once the pest snails run out.
- Be patient. They clear a big pest snail problem over weeks, not days.
- Avoid them in tanks with costly Caridina shrimp, since they can catch molting or baby shrimp.
Frequently asked questions
Will assassin snails eat nerite and mystery snails?
They can. Assassins prefer small snails, but a few working together can kill larger snails, including nerites, mystery snails and rabbit snails. Keep them apart from any snails you value.
Do assassin snails eat shrimp?
Rarely. Healthy adult dwarf shrimp usually get away, but sick, molting or newborn shrimp can be caught. Most cherry shrimp colonies do fine with a few assassins.
Will assassin snails overrun my tank?
No. They need a male and a female, lay one egg per capsule and grow slowly. Their numbers also stay low once the pest snails are gone.
Sources
We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.