How Big Do Assassin Snails Get in Aquariums (Care Tips)

Assassin snails, also known as Clea Helena, are popular additions to aquariums because of their unique appearance and voracious appetite for pest snails. But just how big do assassin snails get in home tanks?

Assassin snails typically grow to around 1 inch, making them relatively small compared to other aquarium snail species.

Their sleek, conical shells and distinctive yellow and brown striped patterns make them a visually appealing choice for many hobbyists.

what does assassin snail eat

Despite their small size, assassin snails are carnivores, feeding on other snails by injecting them with a paralyzing toxin before devouring them.

In this article, we will explore the size of assassin snails in aquariums, breeding assassin snails and care requirements, and how they can be effectively used to control pest snail populations in freshwater tanks.

So, if you’re curious about these fascinating creatures, read on to learn more! 

How Big Do Assassin Snails Get in Tanks?

Assassin snails are generally safe to keep in a planted aquarium. These snails will burrow into the substrate and eat other smaller snails like pond snails or bladder snails.

In a 10 gallon tank, it is recommended to have a minimum of six individuals to ensure they have enough food to eat.

Assassin Snail Lifespan

Assassin snails will even eat the aquarium glass to find snails hiding on the surface. They are also known to eat snail eggs and can help control populations of unwanted pest snails in a tank.

However, it is essential to note that Southeast Asia snails reproduce slowly and may not be able to eradicate a large infestation of snails on their own completely.

It is crucial to remember the size of the tank and the types of snails already present when adding assassin snails as tankmates.

For larger tanks with plenty of hiding spots and live plants, assassin snails can coexist peacefully with other snails like mystery snails or Nerite snails. Additionally, providing meaty foods like brine shrimp, fish flakes, or blood worms can help supplement their diet if there are not enough snails for them to eat.

Average Size of Adult Assassin Snails 

Adult assassin snails are on the smaller side, with an average size of around 1 inch (2.5 cm) in length. However, some larger snails can reach closer to 2 inches (5 cm).

They are easily identifiable by their conical shell that ends in a sharp whorl and alternating black and yellow stripes along the sides of their shell.

In captivity, assassin snails are one of the popular aquascaping communities as a natural way to control pest snail populations. They are relatively low maintenance, requiring a well-oxygenated environment with access to hiding places like caves or plants. 

They are not known to be aggressive towards other tank mates, although they may prey on smaller or slower-moving snails.

Growth Rate of Assassin Snails: How Quickly Do Assassin Snails Grow?

Assassin snails don’t grow incredibly fast, but they will reach adulthood within a reasonable timeframe for a snail. Here’s a breakdown of their growth:

  • Starting Size: Typically sold at a young age, assassin snails start pretty small, around ¼ to 1 inch in length.
  • Adult Size: They can grow to be about 1 inch long when fully mature.
  • Time to Maturity: It takes assassin snails a few months, up to around six months, to reach their full adult size.

While they aren’t the fastest-growing invertebrates, they can effectively manage a pest snail population in your aquarium within a reasonable time.

Factors that Can Affect the Size of Assassin Snails 

Several factors can influence the ultimate size of your larger snails:

  • Genetics: Like most living things, assassin snails inherit genes determining their potential growth range. Some individuals may naturally be on the larger side of the species.
  • Diet: Assassin snails are opportunistic feeders, but their primary food source is other snails. A steady supply of prey like pest snails will provide them with the protein and calcium needed for optimal growth. Pest snails may only reach their full potential size if they are abundant.
  • Water Parameters: Stable water conditions are crucial for healthy shell development. Assassin snails thrive in slightly hard water (7.0 – 8.0 pH, 75 – 80°F) with minimal fluctuations in ammonia, nitrite, and nitrate levels. Improper water parameters can hinder shell growth and limit its overall size.
  • Tank Size: While assassin snails aren’t large creatures, having enough space can somewhat influence their growth. A smaller tank with limited resources might restrict its ability to reach peak size.
  • Competition: Multiple assassin snails in a tank can compete for available prey and resources. If there aren’t enough pest snails to go around, it can affect the growth of individual assassin snails. 

Proper Assassin Snail Care and Feeding Techniques 

Assassin Snails anentome Helena, These carnivorous freshwater snails are known for their appetite for pests, such as Malaysian trumpet snails and ramshorn snails, making them beneficial additions to planted tanks and display tanks.

When caring for assassin snails, it is essential to provide a varied diet that includes meaty foods like bloodworms and algae wafers or algae eaters. Regular water changes are also necessary to maintain optimal water quality in the tank.

Assassin snails should be housed in a filtered and heated tank, as they prefer a stable environment. They can be kept with other snails and dwarf shrimp, but caution should be taken with shrimp species like amano shrimp and cherry shrimp, as the assassins may see them as prey.

When feeding assassin snails, it is crucial to monitor their food intake to prevent overfeeding, which can lead to water quality issues. Providing plants or driftwood in the tank can also help satisfy their natural feeding behavior.

Assassin snails are hermaphroditic creatures, possessing both male and female reproductive organs. They lay single eggs, usually hidden in gravel, on plants, or aquarium glass. Once hatched, the young snails can take up to a year to reach maturity.

With their unique proboscis and two tentacles, assassin snails are fascinating creatures in the aquarium. Their behavior of preying on other snails sometimes raises concerns, but they are generally safe to keep with small snails and shrimp.

Keeping assassin snails well-fed will help prevent them from turning to other tank inhabitants for food. Providing a varied diet and maintaining proper water quality are critical aspects of their care.

With their striking appearance and unique feeding habits, assassin snails can be a valuable addition to an aquatic community tank. Overall, with the proper care and attention, these snails can thrive and contribute to the balance of the aquarium ecosystem.

Will assassin snails overpopulate a tank?

Assassin snails are unlikely to overpopulate. They breed based on prey availability (other snails). With fewer prey, they reproduce less.

How many snails does an assassin snail eat?

An assassin snail typically eats 1-2 snails per month, depending on the prey size. They may also eat scavenged food.

Will assassin snails eat other fish?

No, assassin snails are snail hunters, not fish predators. They’re too slow to catch fish and prefer softer prey. However, they might scavenge on already dead fish.

Are assassin snails good for aquariums?

Assassin snails are good for aquariums with pest snails but not ideal for tanks with cichlids or goldfish. These fish might see them as snacks!

Do assassin snails need a filter?

Yes, assassin snails benefit from a filter. It keeps the water clean and stable, which they prefer. While not essential, a sponge pre-filter on the intake can protect them from getting stuck.


So, how big does an assassin snail get? In conclusion, if you want to enhance your aquarium’s ecosystem and keep unwanted pests at bay, assassin snails are an excellent choice. Their predatory nature and striking appearance make them a captivating addition to any tank. These stealthy assassins are effective at controlling snail populations and adding a touch of intrigue and natural balance to your aquatic habitat. Remember to provide them with a suitable environment, including plenty of hiding spots and well-maintained water quality. 

How big do assassin snails get? If you’re curious about their size, assassin snails typically grow to around 1 inch in length, making them a versatile choice for tanks of various sizes. So, whether you’re a seasoned aquarium enthusiast or starting out, consider adding these fascinating snails to your underwater world. Happy snail-keeping!

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About Me

I am the founder of, a devoted wife and mother, and an avid fish enthusiast. My aim is to assist fellow fish lovers worldwide in understanding how to properly care for and breed their pet fish.

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