Assassin Snail: The Velociraptors of the Snail World

Assassin Snail Infographic

A carnivorous gastropod with a voracious appetite and a fearsome reputation, there’s a pretty good chance you’ve seen plenty of warnings about the assassin snail. But do they deserve the threatening name and even more threatening reputation? Or is the sting in their tale all myth with no truth behind it?

Why don’t we take a look at this multi-named gastropod and find out?

What Are Assassin Snails?

The official, scientific name of the assassin snail is Anentome Helena, which is considerably less threatening. Some even know this critter better as the bumblebee snail, which is pretty much the least threatening name ever… unless you’re afraid of bumblebees, of course. 

This species belongs to the mostly marine Nassariidae family, but the assassin is a freshwater snail. It is a common feature in the aquarium industry because of its ability to keep the populations of other snails in check.

What Do Assassin Snails Look Like?

This snail can look quite striking, which is another reason why people choose to introduce into their home tank setups. With bands of light and dark, usually yellow and brown or black, it’s not hard to understand why it has also earned the nickname ‘bumblebee snail’.

The shells are long and conical in shape rather than the typical rounded garden snail-like design.

How Big Do They Grow? 

With the right conditions, enough food, and a big enough tank, these snails can reach up to 3-inches (7.6 cm) in length. They will only grow as big as the habitat allows, however, so if you have a relatively small tank, you may find that they don’t grow quite that large.

How Long Do Assassin Snails Live?

It’s been reported that these snails can live for up to five years in near-perfect conditions, but in the wild they rarely make it quite that far. They may be predators, but they also have predators of their own.

Where Do Anentome Helena Come From?

In the wild, you’ll find these gastropods in Thailand, Indonesia, Cambodia, and other South East Asian countries. They are originally marine (saltwater) snails from tropical climates, but they are incredibly adaptable and have evolved to survive in freshwater and saltwater environments. In fact, if it weren’t for this freshwater adaptability, humans wouldn’t know very much about the species.

What Does an Assassin Snail Eat?

These gastropods are carnivorous, which means they eat animal material rather than plants. In the wild they tend to eat worms, other snails, and – when other food sources aren’t available – decomposing animal material (carrion), such as dead fish.

When Do They Eat?

These snails are awake and active during the day and night, but more so during the day. They sift through the substrate looking for food, and they’ll also hide themselves in it, waiting for unsuspecting prey to swim by. At that point, they come out from their hiding places and pounce, essentially.

Assassin Snails as Pets: The REAL Deal

As well as looking attractive and different from other freshwater snail types, this gastropod is also great for keeping the populations of other snails down. Being a carnivore, it eats other snails, especially juveniles and smaller specimens.

This species is also relatively low maintenance, which makes them a great species for beginners.

macro shot of assassin snail

How Many Assassins Per Gallon?

You will need a tank of at least 10-gallons for one assassin snail, but many aquarium enthusiasts would recommend a tank size of at least 20 or 30-gallons. This is to ensure that both the snail(s) and other inhabitants are happy and have enough space. These gastropods will only grow to their full capacity if they have the space to do so. They like to move around and explore quite a bit during the day.

These snails can live perfectly well alone and aren’t considered to be an overly sociable species. Although not common behavior, these snails have been known to ‘gang’ together to attack and kill other snails and tankmates, particularly those larger than them.

Water Parameters

All snails are super sensitive to changes in the chemical compounds, temperature, and other water parameters. Nitrite, copper, and ammonia are a definite no-no, so any additions or medications for tankmates that contain them should be avoided. Alternatively, you will need to remove snails and quarantine them until the copper level has reduced back down to zero.

Temperature: 75 to 80 F (23.5 to 26.6 C)

pH level: 7.0 to 8.0

Tank Substrate, Decorations, and Plants

Soft substrates are better for this water-dwelling snail as they like to burrow down into it. This is especially the case when they’re waiting for prey, so you’ll need to ensure it’s at least three inches deep. The more substrate they have, the more they can burrow.

They also like to investigate and explore, so lots of plants, rocks, and driftwood, etc., gives them the opportunity to do that.

Plants are completely safe from assassin snails. They aren’t interested in plants because they’re meat-eaters. Some aquarium enthusiasts use assassin snails to ensure no hitchhikers enter a tank by way of added plant life.


Your assassins will kill and feed on smaller snails in the aquarium, but when those run out, you will need to feed them things like frozen and blanched vegetables, pellets for catfish, and more snails.  


Being a carnivorous species, you will need to be careful of which tankmates you introduce assassin snails to.

Can Assassin Snails Eat Nerite Snails or Mystery Snails?

Yes, they will eat nerite and/or mystery snails alongside trumpet and ramshorn snails, and other species too. The smaller freshwater species are more at risk than the larger ones, but assassins are meat-eaters, so they will eat whatever meat they can get, if they’re hungry.

Can Assassin Snails Kill Fish?

As a general rule, assassin snails will not kill fish – but if they are hungry and you’re not feeding them enough, they are carnivorous, so there is a chance that they could. For that reason, always ensure your snails are fed as much as they need.

Are Assassin Snails Shrimp Safe?

These snails are shrimp safe if the shrimp are bigger than the snails. Even if the shrimp are bigger than the snails, assassins will still attack and feed on the shrimps if there isn’t enough food in the tank to sustain them.

Do Assassin Snails Kill Each Other?

Assassins will usually NOT eat each other, whether that’s in the form of eggs, juveniles, or adults. If there isn’t enough food in the tank to sustain all inhabitants, however, it can’t be ruled out that this species of gastropod won’t turn on its own and cannibalize them.

Assassin Snail Breeding Guide

Unlike the prey of this snail, assassins are not a fast-breeding species that will cause problems in your tank. They breed slowly, laying just one egg at a time, although there are sometimes clusters of single eggs laid closely together.

Can Assassin Snails Reproduce on Their Own?

No, they’re not hermaphrodites. In order for this snail to breed you must have at least one female and one male in the tank. If you have two (or more) females or two (or more) males, they will not be able to ‘switch’ gender and mate. They can’t self-fertilize, either. Copulation can take many hours.

Assassin Snail Eggs

Yellow colored eggs are usually attached to something, such as the glass of your tank, rocks, plants, or decorations and ornaments. They are laid singularly, and they’re encapsulated in a tiny pouch that is almost completely transparent.

The eggs take around eight weeks to hatch, and the juveniles immediately dive down to the substrate, where they hide until they’re big enough to not become food for other tankmates. This can take several weeks and, in some cases, even months.


Are Assassin Snails Nocturnal?

Some assassins might be nocturnal but most of them are more active during the day than at night. They move more slowly and less frequently at night. During daylight hours, however, you might be surprised by just how fast and how much these bumblebee-looking guys can move around.

How Will I Know if Assassin Snails Are Killing Other Snails?

If you have an assassin snail in your tank, it will only take a few days before you spot an empty shell in the tank. That empty shell will be all that remains of the assassin’s meal. You may also notice that algae starts to build up a little more, because the algae-eaters are being eaten.

Where Do Assassin Snails Hide? And Why??

Yes, they do hide. They will burrow under the substrate and wait for prey to pass by, and they’ll also burrow down and sift through the substrate looking for something to eat.

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