Assassin Snail – Habitat, Care, Feeding, Tank Size, Breeding

The assassin snail (Clea helena) is popularly used by aquarists to control snail infestations. As the name suggests, these snails are predators, and they will prey on snails like ramshorn and trumpet snails.

The snail is, however, harmless to shrimp and fish. Assassins are easy to look after, and they will be fine as long as the tank is clean and free of copper.

Assassin Snail Appearance

The assassin snail will grow to 0.7-1.25 inches, although captive specimens are typically smaller.

It has a conical shell with yellowish and dark brown bands, which have earned it the name bumblebee snail. Some assassins have been identified without bands on their brown shells.

There is a muscular ‘foot’ in the shell, which contracts for the snail to move around. The operculum is located on top of the foot, near the snail’s backside.

When buying an assassin, ensure it has two tentacles since some of them are kept with fish-nippers. The eyes lie at the base of each tentacle. The shell should also be smooth and free from cracks and splits.

You want assassins that are active and healthy, and they should be fixed on hard surfaces. Avoid individuals who lay motionless at the tank’s bottom as they are likely sick or stressed.

The assassin has a rasping radula that they use to erode the shell of other snails. They will slowly grate away flesh and blood and weaken a prey. Several assassins have even been seen ganging up on larger snails.

Assassin Snail Tank Requirements

What is the minimum tank size for assassin snails? Are assassin snails compatible with plants? Let’s find out how to keep these snails happy.

Tank Size

While you can keep assassins in small tanks, it is advisable to use large aquariums. They are often housed in 10-gallon tanks, but you should consider that they do not breathe air like other aquarium snails.

The snails are sensitive to inconsistent water parameters, and it is harder to maintain stable conditions in a small set up. You also need to provide assassins with adequate populations of freshwater snails, which is only possible in a big tank.

Assassins thrive in groups of five or six, and you can keep them comfortable in a 30-gallon aquarium. The aquarium should be tightly covered as assassins are notorious escapers. Cover filter intakes as well so that they do not get trapped and injured. 

Plants and decoration

Assassins are perfect for planted tanks because they are strictly carnivorous. If you have lots of plants in your setup and you want to keep snails, consider getting assassins.

They are also not fussy about decorations, but you can provide objects for them to climb and lay their eggs on.

These snails are active diggers, and a sandy substrate will present the ideal bottom.

Assassin Snail Water Conditions

Assassins are native to Southeast Asia, where they inhabit small water bodies. They prefer shallow and freshwaters with a slow current and are commonly found in ditches and ponds.

These habitats have muddy or sandy substrates and are slightly alkaline. You should replicate these conditions in your tank.

A temperature range of 70-81 °F will mimic the warm tropical waters in their natural habitats. The PH should be between 7.0-8.0.

Stability is vital when it comes to assassin snails. Nitrite and ammonia levels should be kept at 0ppm, and regular water changes will keep nitrate levels low.

Assassins need to be acclimatized slowly to any new environment. The tank should be well established, cycled, and stabilized before the snails are added. It should also be well-filtered and aerated so that they get sufficient oxygen.

Poor water quality will also affect the health of their shells. Look out for white spots that indicate a parasitic infestation and ensure that temperatures do not become too low. Add calcium supplements to the water to strengthen assassin shells.

Assassin Snail Diet and Feeding

Assassin snails actively prey on other snails. While snails without an operculum like ramshorn snails are easier to attack, assassins will also target specimens with an operculum like trumpet snails.

Larger snails like Japanese trapdoor snails, ivory snails, nerite snails, and mystery snails are generally safe, although it may depend on how hungry the assassins are. Although adult snails will be spared, assassins will likely target their young ones.

Assassins lay still in the substrate and wait for prey. They will extend their proboscis and attack another snail in groups. Assassins will easily eradicate populations of Malaysian trumpet snails, ramshorn snails, and other snails.

You can maintain a snail breeding tank, or buy some from local pet stores. One or two snails a day are typically enough for a group of assassins.

In the absence of snails, you can provide high-protein fish pellets, flakes, and algae chips. It is thought that the growth rate of assassins is halted if their food is not rich in protein.

You can use live foods like brine shrimp and bloodworms to diversify their diet.

Assassins will also scavenge for uneaten fish food and meaty debris. They can eat shrimp fry and soft snail eggs.

Assassin Snail Tank Mates

Assassin snails are incredibly slow, and they are a poor choice for aquarists who want some activity. They like to feed at night, and you can miss them during the day.

They have an impressive sense of food, and they will emerge when you provide meals, even if it is daytime. The rest of the time is spent buried in the substrate, waiting for snails.

Assassin snails are peaceful towards their kind, and they prefer to be kept in groups. When choosing fish, avoid aggressive bottom dwellers. You can keep them with peaceful scavengers like the otocinclus catfish or the cory catfish.

Assassins will get along with most peaceful community fish, including neon tetras, guppies, cherry barbs, and celestial danios.

Avoid aggressive varieties like cichlids and goldfish that will injure the snails. Do not keep assassins with fish-nippers who may damage their fragile tentacles.

The snails are commonly kept with freshwater clams, amano shrimp, bamboo shrimp, viper shrimp, and ghost shrimp. Ensure that any shrimp you keep is larger than the assassins.

Assassin Snail Breeding

Unlike most gastropods, assassins are not hermaphrodites. It is, however, difficult to tell males and females apart, and you should buy several of the snails to increase the likelihood of having both sexes.

Although assassins are easy breeders, they are slow to reproduce. You can induce mating by providing protein-rich meals and warm temperatures.

A copulating pair will lock together for as long as 12 hours. The female will then detach and deposit one egg at a time on solid objects.

It takes about 20-30 days of the assassin eggs to hatch. The water conditions influence the incubation time, and the eggs will hatch quicker if there are a lot of minerals.

The juvenile assassin will wiggle out in about an hour, with a shell that is 5 mm in length. The little snail will burrow itself into the substrate immediately, and only come out occasionally to forage for food.

Juvenile assassin snails will attain sexual maturity at six months, after which they will be spotted regularly.

The snail’s slow reproduction rate prevents it from becoming a pest. They can, however, be hard to completely eradicate from a tank because they like hiding in the substrate.


Assassin snails are famously used to control pest snail infestation. They will ruthlessly attack smaller snails like trumpet snails and ramshorn snails but will leave fish alone.

You will need an aquarium with stable parameters to keep the assassins since they are vulnerable to bad water quality. Keep several of them together, and invest in a large tank.

Snails   Updated: June 26, 2020
avatar Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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