Assassin Snail: Definitive Guide To This Pest Controller

The Assassin Snail is a very unique aquarium snail.

Most aquarium snails will feed on algae or plants, but this carnivorous snail feasts on other snails.

They are nature’s clean up crew and one of the only freshwater predatory snails. If you have pests in your aquarium then these snails are one of your best options to get rid of them.

Do you want to add a few Assassin Snails to your tank?

Keep reading to learn everything you need to know about these snails…

Assassin Snail

About Assassin Snails

Assassin Snail On Leaf

The Assassin Snail, Clea helena, is a freshwater snail from the Nassariidae family.

This small mud snail comes from Southeast Asia and has earned the nickname of Bumblebee Snail because of its brown and yellow shell pattern.

They are one of the only predatory aquarium snails around and are commonly used as natural pest control.

Assassin Snails are easy to care for and aquarists of any skill level can keep them.

A good general rule to follow is that your Assassin Snail should be the smallest and slowest snail in your aquarium.

They typically grow to around 1 inch and have a lifespan of 2-3 years. Compared to other gastropods they develop slowly and only reach maturity at 6 months of age. Typically smaller pet shops will not carry this exotic snail, however you can find them online from most aquarium suppliers. The average price is $2.50-$4.50 per snail.

Assassin Snail
Other Common Names: Bumblebee Snail
Scientific Name: Anentome helena/Clea helena
Family Name: Nassariidae
Distribution: Southeast Asia
Size: 0.80-1 inches
Color: Grey body with brown and yellow or solid brown shell
Care Level: Easy
Temperament: Peaceful
Lifespan: 2-3 years
Minimum Tank Size: 10 gallons
Tank Mate Compatibility: Peaceful medium sized fish, schooling fish and large snails

Pros and Cons


  • Natural pest control for tanks.
  • Community tank compatible.
  • Cleans algae and detritus as well as pests.
  • Can be kept in tanks of just about any size.
  • Will not attack fish.

  • Sensitive to water changes.
  • Can be eaten by predatory fish.
  • Difficult to breed.
  • Can clash with other bottom dwellers.

Assassin Snail Appearance

Clea helena

Assassin Snails are related to whelks and they have the same grooved conical shells.

Their shell will have up to 8 whorls, with about 3 bands per whorl. It is a mustard yellow color with muddy brown bands. This color allows them to blend into the muddy substrate in the wild.

This snail’s body is translucent grey, but can be faded yellow near the shell.

Just above the snail’s head, a tubular siphon protrudes from the tip of the shell. This appendage is used to detect movement and vibration of potential prey. When the snail has found its snack, it extends its long proboscis to hold the prey in place. Then they will pierce the captive’s body with their sharp radula.

The radula is a saw-like tongue that is used to bore through prey.

This snail also has a muscular foot, two long spindly eyestalks and 2 feelers in between the eyestalks.

A muscular foot is a defining feature of every gastropod. The foot, which is located on the snail’s abdomen, allows the snail to move across the substrate via muscle contractions.

You can expect your Assassin Snail to reach around one inch, however sometimes they have been known to exceed this.

Unlike many other snail species (that are hermaphroditic) this particular snail has two genders. However, it is impossible to tell the males and females apart by looking at them.


The Assassin Snail can come in one of two color varieties:

  • Yellow and brown: This is the typical color variety. A mustard yellow shell with 3 or 4 muddy brown bands on each whorl.
  • Brown: This is a particularly uncommon color form. The shell will be muddy brown with no yellow at all.

Assassin Snail Breeding and Eggs

Assassin Snail Eating Algae

It can be difficult to breed the Assassin Snail because it is so hard to tell the males and females apart.

However if you have a large enough group of snails then they will likely breed on their own. If you are planning to breed your snails, it is best to have a group of 6 to 8. Unlike many other aquatic snails, this snail does not need an aquatic environment to reproduce. They spawn on the sides of rocks and logs.

The first thing you need to do is isolate your breeding group in a tank of their own.

In this breeding tank raise the temperature between 77-80°F. You should also fill the tank with rocks and logs for the snails to lay their eggs on.

Snails that are looking to breed will cluster together in large groups. Mated pairs will remain attached to one another while copulating.

Breeding occurs about 12 hours after the snails have paired off.

They will only lay one egg at a time but can spawn multiple times.

The eggs will take about a month to hatch, and even then, you will not see the juvenile snails until they have matured. They will bury themselves in the substrate and stay there for about 6 months.

Because of this the substrate in your nursery tank should be enriched with microbial colonies that the juveniles can feed off of.

Once your Assassin Snails have matured, they will be ready to join the rest of your aquarium community.

Tank Mates

Assassin Snail In Freshwater Aquarium

In the wild these reclusive snails keep to themselves and do not associate with any of the native wildlife. Their ecosystem dynamics are not very well understood.

However in the aquarium they are surprisingly passive for a predatory snail.

They will only attack those that are smaller or slower moving than themselves.

Any medium sized peaceful fish or fast moving schooling fish are safe. These include Zebra, Pearl, Giant and Celestial Danios. If you want to include a few Gouramis in your community then the Sparkling, Pearl and Dwarf Gouramis are the best ones.

Fast moving Cardinal and Neon Tetras that congregate in large schools are safe too.

If you are keeping the snails in a paludarium then you can include turtles and other herbivorous reptiles.

It can be difficult keeping other bottom dwelling invertebrates with any predatory snail, but larger snails and other large invertebrates should be perfectly fine. Nerite Snails, Apple Snails and Mystery Snails can all be kept with Assassin Snails.

You should avoid any large or aggressive fish.

Even the peaceful Discus and Angelfish are likely to snack on your snails.

You should also avoid any larger bottom dwelling fish such as the Pleco Catfish. Very small, shy nano fish like Chili Rasbora are also best kept away.

All small invertebrates are at risk for being eaten by your snails. These include Cherry Shrimp, Grass Shrimp and any small snails.

Crabs, crayfish and larger shrimp should be avoided as well.

How Many Assassin Snails Should I Keep?

Assassin Snails can be kept together in groups of up to 6.

They should only be kept in larger groups if you plan on breeding them.

Most of the time they will ignore each other and keep to themselves. The only exception to this is when they are ready to mate. If they find something tasty at the bottom of your tank they may congregate in large groups to share the pickings.

You can keep lots of groups of these snails together in a larger tank. But if you do, do not be surprised if you find a few of their eggs alongside your rocks and other decorations.

Assassin Snail Care Guide

Assassin Snail Substrate

Anybody can care for an Assassin Snail and they can be kept in a tank of just about any size.

The biggest concern with this snail is their brittle shell.

This can happen when the snail does not have enough calcium in their diet, or the water quality is poor.

Snail shells are made out of calcium carbonate, which is readily available in waters with at least a medium salinity. When the water is too acidic or too high in CO2, the calcium carbonate dissolves and their shells will break.

You should regularly monitor your tank’s pH and make sure it does not dip below 7.

Also be aware of excess CO2 in your water column which can happen when your tank is too dirty or over fertilized.

The Assassin Snail is can also carry trematodes (flukes).

These parasitic worms do not hurt snails, but they can cause illness and infection if they spread to the fish in your tank.

The snail serves as a host for the worm during its life cycle. When the worm leaves the snail’s body, it can infect your fish. A trematode infection causes redness and irritation on the fishs’ fins, scales and gills. If a fish is rubbing itself against the objects in your tank, it is likely they have a trematode infection.

Remove both the infected fish and all of the snails in your tank if a trematode infection occurs. Both the fish and the snail will require an anti-fluke treatment which you can buy at an aquarium supplier.

Key Facts:

  • Experience Required: Freshwater fishkeeping
  • Nicknames: Bumblebee Snail
  • Color Forms: Yellow and brown, solid brown
  • Size: 0.8-1 inch
  • Tank Size: 10+ gallons
  • Tank Temperature: 70-80°F


Assassin Snail On Tank

In the wild these predatory snails feast on other smaller snails and worms.

This will not change in captivity.

Your Assassin Snail will usually be able to find food on their own (especially if your tank has a problem with worms and other small pests).

However, free feeding does not always provide your snail with everything that it needs to stay healthy. It is best to provide your snail with a few other things as well.

If your tank is low on natural prey you can purchase live feeder snails and bloodworms. Simply place them at the bottom of your tank and let your snails hunt them on their own.

The snails will only need to feed twice a day – they will come out to hunt just after sunset every night.

You can purchase snail pellets and snail flakes from an aquarium supplier to supplement a diet of live prey. All pellets and flakes should be high in protein.

These snails will also scavenge on any fish foods that make it to the bottom of the tank.

Water fleas and brine shrimp can be given as a bit of extra protein from time to time.

After protein, calcium is the most important nutrient in a snail’s diet. It helps to keep their shells healthy and strong. Include calcium supplements in your snail’s diet and provide crushed snail shells or clam shells for them to snack on.

Please also ask do assassin snails eat algae?

Yes they do eat algae.

What Food Can They Eat?

As bottom feeding scavengers they are able to eat all kinds of foods. Here is a list of all of the things that your snails can eat:

  • Live snails
  • Bloodworms
  • Flatworms
  • Polychaete worms
  • Small feeder fish
  • High protein flakes
  • Algae
  • Crushed clam shells
  • High protein pellet
  • Detritus and dead plant material
  • Brine shrimp
  • Crushed snail shells
  • Carrion

Tank Set Up

In the wild these snails live along the banks of rivers, streams and creeks in Indonesia, Malaysia, Laos and Cambodia.

There is little to no water flow in their natural habitat, and the temperatures tend to hit highs of at least 75°F.

They come out after sunset to hunt so they are used to very low light. During the day they will stay concealed under rocks and leaves.

Like most snails, they prefer wet environments and tend to show themselves after heavy rainfall.

So how should you set up their tank?

Assassin Snails prefer to make their homes in sandy or muddy substrate. If you are keeping a paludarium you must keep the mud damp at all times to stop your snails from drying out.

You will need to keep the temperature between 75-80°F – use a basic heater for tropical freshwater aquariums.

Because the currents in your tank should be very low you do not need a powerful filter – a small internal under gravel filter or HOB filter works just fine.

You will need to maintain a pH range between 7.0 and 8.0. This is a freshwater snail, but higher salinities lead to stronger shells (according to this study). For this reason you should keep a hardness between 12 and 15 dGH.

As for light, any light intensity is fine as the snails will just avoid the light on their own. Your snails will only be active when the lights are low to moderate.

Finally, for the decorations.

Rocks, logs, and wood make the perfect spots for these little snails to hide. In a paludarium, any leaf litter or moss (like Java Moss) that you mix in with your substrate serves as extra shelter for your snails.

Your substrate should be enriched with plant material. Laying some wet leaves or moss over your substrate should help. They are not too fussy about plants and will accept just about any of the most popular aquarium plants.

Anubias is one of the best plants for an Assassin Snail tank, especially in the terrestrial areas of a paludarium.

Liverworts and ferns are two good plants that grow in the snail’s natural habitat. You can also float frogbit and duckweed along the surface of your tank for an authentic river effect.

Tank Parameter Requirement
Minimum Tank Size: 10 Gallons
Tank Type: Freshwater
Temperature: 70-80°F
pH: 7.0-8.0
Hardness: 12-15 dGH
Flow: None to low
Substrate: Sand or mud

What Size Aquarium Do They Need?

A group of 5 or 6 snails can live happily in a tank of at least 10 gallons. As usual though, the bigger the better if you are keeping a diverse community of fish and invertebrates.

A 20 gallon tank will comfortably host up to 12 snails.

Typical Behavior

The Assassin Snail is surprisingly peaceful for a predatory snail.

They will simply ignore anything that is too big or too fast for them to eat.

In general this is a solitary snail that prefers to keep out of the way for most of the day. They are only active at night when they come out to hunt. While on the hunt you will see them extend their long siphon to scope out its prey.

They have eyestalks and feelers which let them detect light and vibrations in the environment around them.

This allows them to avoid high light environments and also lets them detect any suspicious movements that may indicate a predator.

If you watch you snail in the tank you may find them climbing up the glass or on the decorations in your tank. However they will never venture too far above the bottom levels of the tank.

Overall, when they are not out hunting they are very secretive and will hide in wet mud or under rocks and leaves.

Assassin Snail On Rocks

Species History

Not much is known about this snail’s history as they have not been studied extensively in the wild.

What we do know is that they were first discovered in 1847 in Indonesia.

Their first scientific name was Anentome helena, however they were also given the name Clea helena – both are still accepted. The US Fish and Wildlife service lists the species as Anentome helena.

Before 2016 they were classified under the Buccinidae family. However since then they were moved to the Nassariidae family. This distinguishes the freshwater Clea snails from the mostly-marine Buccinidae.

The snail was first introduced to home aquariums sometime in the 2000s.

They were sold as a natural pest control.

To this day, many aquarists use Assassin Snails to remove unwanted small pests from their tanks. It is much safer to use these snails than to use chemical pest control.

Fun Facts

  1. The Assassin Snail is almost completely blind. Their rudimentary eyes can only detect light, and they need their other appendages to help them get around.
  2. These snails are commonly used as pest control in home aquariums.
  3. You can often tell how old a snail is by looking at its shell. Older snails tend to have visible wear or holes in their shells.
  4. These snails can live in paludariums as well as aquariums.
  5. Assassin Snails have been found along the banks of the Kranji Reservoir in Singapore, outside of their natural range. They are thought to have escaped from farms where they are raised for the aquarium trade.
  6. Their banded shell acts as camouflage in the wild. The mud colored bands allow the snail to blend in with the substrate along the river banks.

Should You Get Assassin Snails?

If you have a pest problem then the Assassin Snail can be a big help.

This peaceful but efficient predator can get rid of any small and unwanted critters in your tank. They may even help clear out a little bit of algae too.

Despite their name they are actually very peaceful and tend to keep to themselves.

They may not be very fun to watch, but they make up for it by working hard to keep your tank free of any nuisances.

Because they only go after prey that is smaller and slower than they are, you can safely keep them with most tropical fish.

You can certainly benefit from keeping a group of these useful snails around. Has an Assassin Snail helped you get rid of pests in your aquarium?

Let us know in the comments below…