Assassin Snails and Betta Fish

Snails are generally fairly robust animals, that often handle an array of different water conditions. This, combined with their peaceful natures, has made them popular as companions for reasonably peaceful fish like the Betta.

Unlike many other snails, the assassin snail isn’t an opportunistic omnivore, but an active predator. It actively pursues, and eats, other invertebrates. Thankfully it still makes a great companion for bettas!

As a biologist specializing in snails, I’ve had plenty of experience with these snails, and I’d love to share some advice for keeping them and cohabiting them with betta fish. Let’s get into it.

Key takeaways

  • Assassin snails are carnivorous snails that can coexist with betta fish in the same tank, as long as they have enough food and hiding places.
  • Assassin snails are native to Southeast Asia and have a distinctive conical spiral shell that can vary in color from light to dark brown.
  • Assassin snails feed on other snails by following their mucus trails and can help control pest snail populations in the aquarium. They also need calcium and magnesium for their shell health.
  • Assassin snails are hermaphroditic and can self-fertilize their own eggs, which they lay in a calcium sac on a flat surface. They rarely overpopulate their tanks, but their population should be monitored.
  • Assassin snails prefer water with a neutral pH and a temperature range of 68-82℉ (20-28℃). They are nocturnal and may try to escape from the tank, so a tight lid is recommended.

Natural Habitat And Origin

Assassin snails are native to Southeast Asia, where they live in a variety of freshwater habitats, including streams, rivers, lakes, and ponds. They tolerate both shallow and deep water, but prefer water with a neutral pH and a temperature range of 68-82℉ (20-28℃).

Although assassin snails originated in Southeast Asia, they have been introduced in many countries as an effective biological control method for other snail species that may be considered pests. However, these snails can easily become invasive and have done so in many parts of the world. 

What Is The Appearance Of An Assassin Snail?

Assassin snails have a very distinctive appearance which includes:

  • Shell Shape: Conical spiral 
  • Shell Coloration: Varies between light brown and dark brown. 
  • Shell Texture: Smooth and silky
  • Size: Small, between 1-1½ Inch (2.5-3 cm)

They also have the following features:

  • A soft light gray body that may have darker spots or stripes
  • Two short, thick antennae, which they use to sense their surroundings
  • Muscular feet, which they use to move around
  • A respiratory siphon used to get oxygen from the water. Instead of breathing through their entire bodies, water snails have a siphon that allows them to draw water into their shell, where their gills absorb oxygen and release carbon dioxide.

Assassin Snails Taxonomy

The Assassin Snails, is a species of carnivorous snail which scientists classify into the following taxonomical phyla:

  • Phylum: Mollusca
    • Class: Gastropoda
      • Order: Neogastropoda
        • Family: Nassariidae
          • Genus: Anentome
            • Species: Helena

It’s worth noting that taxonomists have recently proposed adding an additional phylum, the subfamily Anentominae, to this list.

Assasin Snail Behavior

Assassin Snails are natural-born predators known for their aggressive feeding behavior. Despite their aggressive feeding habits, these snails are generally peaceful. It won’t hesitate to eat other snails when hungry, though.

They’re nocturnal animals, which means they are more active at night than during the day. However, these snails are generally quite active and may try to escape from the tank, so keeping the tank tightly closed is crucial. 

How To Prepare Your Aquarium For Assassin Snails?

Setting up a tank for assassin snails is relatively easy. Here are some tips to ensure your tank is ready for your new snails:


Assassin snails aren’t particularly picky about plants, but prefer shorter plants that don’t shade the tank too much. Floating plants such as water lettuce are an excellent choice as plants that grow near the surface of the water provide a spawning ground for assassin snails.


Assassin snails can dig up the plants if the substrate is not dense enough, and some of the best choices include:

  • Coarse sand
  • Filter sand
  • Coarse gravel

It is important to avoid substrates that can release limestone into the water, as this can negatively affect the pH of the water.

Water Parameters

Assassin snails tolerate a wide range of water parameters, but generally prefer water meeting the following criteria:

  • Temperature: 68-82℉ (20-28℃)
  • pH: 7.0-8.0
  • Water hardness: 6-12 dGH

Other Considerations

  • Light: Assassin snails don’t need a lot of light, but it’s important to provide some light to allow the plants to grow. 
  • Filtration: Must be strong enough to keep the water clean, but not produce strong currents that could harm the snails.
  • Shelter: Provide plenty of hiding places like logs, rocks, or empty shells.

Diet In The Wild And Diet In An Aquarium

Assassin snails feed on other snails by locating and following their mucus trails. 

In the wild, their diet consists mostly of small snails, though they will occasionally consume larger snails. In an aquarium, they will eat any small snail, including other assassin snails. 

They’ll also eat other living things, like shrimp and fish eggs.

They don’t feed on plants, but may dig up plants while looking for snails. Since these snails are carnivorous, it’s vital to ensure that there are enough snails so that the assassin snails can feed properly.

Finally, it is worth mentioning that assassin snails have a voracious appetite. If you’re maintaining more than one snail species in the same tank, ensure that there are adequate space and resources for all the species in the aquarium.

These snails also need a source of calcium and magnesium in their diet to help with the development and maintenance of their shells. An excellent way to provide this is by adding a cuttlefish bone to the aquarium.

Assassins Snails As A Way To Control Other Snail Species

Assassin snails are popular in the aquarium hobby as a means to control the populations of other snail species.

They’re natural predators of virtually all the snail species that breed heavily. However, when using assassin snails to control other snails, it should be done in conjunction with other methods like manual removal. 

Assassin snails can also be an excellent addition to aquariums that contain ornamental snails, as they help control overpopulation by eating newly hatched and young snails.

However, you should monitor the assassin snail population closely to ensure that they don’t overwhelm the ornamental snails. I advise a ratio of one assassin snail for every five to ten gallons of water in the aquarium.

How Do Assasin Snail Reproduce In A Fish Tank? Can They Cause Snail Overpopulation?

Assassin snails are hermaphroditic, having both male and female reproductive organs. What’s interesting about this species is that it’s self-fertile, and can fertilize its own eggs. In many snail species, individuals are hermaphroditic but require a second snail to breed successfully. 

Assassin snails can reproduce at sexual maturity, which occurs around six months of age. They engage in a lengthy mating ritual that can last for several hours after which they lay their eggs in a calcium sac on a flat surface at the bottom of the aquarium. 

Each sac contains 20 to 40 eggs which hatch in two to four weeks, depending on the water temperature.

Assassin snails rarely overpopulate their tanks and are used as a natural way to control other snail populations. Since they feed on other snails, they help maintain balance in the tank and prevent other snail populations from growing out of control.

However, since a single assassin snail can reproduce on its own, controlling the snail population is essential.

Assassin Snails and Bettas

Assassin Snails generally make great companions for everything except really tiny fish and other invertebrates. Bettas are a fantastic option, since the two animals stay out of each other’s way, and betta fish are too large for assassin snails to eat.

You should also be careful not to place them in tanks with fish like cichlids and pufferfish that habitually eat snails. That said, I’ve seen mouthbrooders and severum try to eat assassin snails without any success. These are extremely hardy animals.

In general, it’s best to do a lot of research before keeping assassin snails with any type of fish. You should also monitor new additions to the tank carefully to see if there are any signs of aggression.

Where To Buy Assassin Snails

In the US, assassin snails are readily available. You can try any of the following and should acquire them with ease:

  • Asking at your LFS (Local Fish Store)
  • Buying from private breeders in your area
  • Buying from a general pet store
  • Ordering from an online store like Amazon or eBay
  • Posting a request on a regional fish forum

These animals are extremely popular as a means of biological control, and you should find them easily. If you decide to order online, only buy from vendors with a good online reputation. You should also bear in mind that it’s illegal to release these animals into the wild, as they are considered an invasive species.


Assassin snails are an excellent way to control pest snail species, though they shouldn’t be your sole means of control. They have laid-back personalities (despite their predatory nature), which makes them an ideal co-habitant in a betta tank.

If you’re looking to add a bit more life to your betta tank, or just to get an interesting new species, I’d definitely recommend trying assassin snails.

About the author

Hi, I am Marcelo.

I am fascinated with researching and writing about fish.
I have a degree in biology (herpetologist) and animal science (zootechnics) specializing in ornamental fish and South American biotopes.

You can find the articles I wrote here.

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