Anentome helena – Assassin Snail

Anentome helena or Assassin Snail can be a great addition to the smaller aquariums. Their diet consists of other snail species, keeping their numbers in control.


Anentome helena – Assassin Snail

Anentome or Clea helena was first described in 1847 by Meder in Philipi.

The scientific name seems a bit unclear. In aquarium related websites and books it is often referred to as Anentome helena but actually it is Clea. The genus name is Clea, to make a differentiation between the Clea species from Asia and Africa they gave the sub-genus names Anentome for the Asian Clea species and Afrocanidia for the African Clea species.

Their common name is a good indication for their diet: Assassin Snail. Despite them already being described in 1847 the first imports to Europe started only in 2006.


The Assassin Snail has a pointy twisted shell. In aquariums the most common colour is yellow/brown. Each twist has these two colours circling into the point of its shell. The total length of the shell can grow up to 2 centimetres but usually reaches just over 1,5 centimetres. In total this snail can reach a length of around 3 centimetres.

The shell is heavily ribbed at each rotation. The tip of the shell is usually broken or worn so there is no reason to worry about that if you have Assassin Snail looking like that. By the number of rotations you can roughly see how old the snail is. More rotations means an older snail. The body itself is a peppery grey/green.

You can tell males from females by comparing them. Females are a bit bigger and plumper build. The black stripes are wider with females.

Besides the well known yellow/brown Clea Anentome helena light green and light brown varieties are available. They can reach a maximum age of around 5 years.


Clea Anentome helena can be found in a vast distribution area in South East Asia. They live in Thailand, Indonesia and Malaysia. Other members of the Clea family can mostly be found in salt water, the Assassin Snail however can only be found in fresh water.

They live in flowing waters of lakes and ponds with muddy or sandy substrates.

Anentome helena distribution area
Anentome helena distribution area – CC BY-SA 3.0 – Michal Maňas –


The diet of the Assassin Snail – won’t be a surprise. Their meal consists mainly of other snails. Most other snails species are eaten except other Clea Anentome helena.

The Assassin Snail can hunt snails in two different ways. They can burry themselves in the substrate, only the protruding mouth can be seen like snorkel. If an other snail passes by the Clea Anentome helena grabs the snail.

The second method is more active, the Assassin Snail chases other snails until it catches them.

No poison

Contrary to popular belief, they do not inject poison. With their Siphon they locate their prey. With their strong foot they hold on well to the prey. They are now looking for the opening of the snail. Their mouth contains a retractable proboscis, which is a kind of trunk that protrudes in search of the snail’s flesh. The tip of the proboscis contains a radula, a kind of rasp tongue. The radula is studded with small teeth that act like a chainsaw. With this they scrape the meat off their prey. The prey is thus eaten alive. The video below, contains a very good explanation of how they eat their prey.


Apple snails and Red-rimmed melania

Large snails like adult Apple snails are not always safe for the Clea Anentome helena. They team up to take on a bigger snail together. They will attack, kill and eat the bigger snail as a group. Red-rimmed melania are also on the menu. They are probably not at the top of the wish list. The Assassin Snail prefers to eat other snails or food. The Red-rimmed melania cannot always be eaten in its entirety, the cochlea is fairly deep and strong. The residue is then digested by fungus and bacteria. On average an Assassin Snail eats one snail a day.

Anentome helena feeding on Red-rimmed melania:


Besides snails they will also eat planaria. Planaria are small wormlike creatures that can sometimes become a real menace. Because the Assassin Snail eats planaria you can prevent an outbreak of these pests or even get rid of them in an aquarium friendly manner.

As soon as there are no living snails left, Clea Anantome helena falls back to feeding like a scavenger, eating dead fish, detritus and organic waste. Living plants are left alone so you don’t have to worry about that.

The Aquarium

A small snail-like the Clea Anentome helena doesn’t need a large aquarium. A 30-litre tank will do just fine. They prefer sand as a substrate because of their hunting habits.

They prefer a water temperature between 20 and 27 degrees Celsius. They can handle a pH between 6.0 and 8.0 and GH between 8 and 15.

Breeding Anentome helena

Clea Anentome helena only lays eggs if they have plenty of living snails to feed on. You will need both males and females to breed them so keep them in a group of at least five to get a better chance of having both sexes.

They will lay one square egg packet a time on a rock or other hard surface. Each packet contains just one egg.

As soon as the egg hatches the young Clea Anantome helena disappears in the sand. You probably won’t see them for the first couple of months. After 4 to 8 months the snails are sexually mature and can reproduce again.


If you have too many snails you will have to get rid of the cause of this problem (usually overfeeding). Additionally, you use some Assassin Snails to prevent new outbreaks of pest snails. They can also be used to get rid of planaria without using medicine or chemicals. On top of that, it is also a nice looking snail that will stand out in the smaller aquaria.



John de Lange

Copyright images

John de Lange

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