How Big Do Mystery Snails Get? Complete Guide To Mystery Snails

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Mystery snails are such fun, colorful little creatures to keep in the aquarium. They even eat algae, so you have the added bonus of a helpful tank cleaner! If you are looking for an entertaining, low maintenance addition for your tank, mystery snails might be the perfect fit for you. Not sure what exactly mystery snails are? That’s okay, they are a “mystery” after all! Read on to learn all about mystery snails and exactly how big they might grow in your tank. 

how big do mystery snails get

What Is A Mystery Snail?

As one of the most popular kinds of snails kept by aquarists, mystery snails also go by the name “common apple snail”. They have a common spiral shape to their shell that is found in many snail species.

They usually come in white, yellow, and brown colors of different shades. Striped and patterned snails are rare and are only found on albino mystery snails. In the wild, mystery snails are found in South America in places like freshwater swamps, rivers, and ponds. They are versatile and can survive in different environments which makes them a popular choice for aquariums.

Types Of Mystery Snails

It is thought that mystery snails got their name because nobody knew what they were upon discovery. Today, we know there are two kinds of mystery snails in aquarium keeping: Pomacea bridgesii and Pomacea diffusa. Here are the differences:

Pomacea bridgesii: 

  • Rare species found along the Rio Grande river
  • Not common in the aquarium trade
  • Larger in size — up to 65mm in height

Pomacea diffusa: 

  • Common species found throughout the Amazon river
  • Common in the aquarium trade
  • Smaller in size — about 45 mm in height —and darker in color

Can Mystery Snails Live Out Of Water?

Mystery snails have gills to breathe water and lungs to breathe air. They have a tube-like body part called a siphon that they use to inhale air. However, they can’t be outside water forever and can only survive a few hours.

If they stay out of the tank for too long, they will dry up and die. This is why it is important to have a lid on your aquarium if you plan to purchase snails. 

To prevent drying, snails have a hard operculum at the opening of their shell. They can open and close the operculum when they are feeling threatened, or when they want to preserve water. If you find the escaped snail before it is too late, their operculum may have just saved them from dying. 

Mystery snails also breed outside of water. They crawl out of the tank and lay their eggs just above the surface of the water. If you do not wish to have baby snails, this is another good reason to have a lid on your tank. 

How Big Do Mystery Snails Get?

how big do mystery snails get

Beginner hobbyists may have smaller tanks not suitable for many organisms. It’s always important to know how big an animal will get before adding it to an aquarium, but it’s especially important for smaller tanks. 

So, how big do mystery snails get? The answer is — not very big. Most mystery snails will grow to about two inches in diameter. Even though they are small creatures, they are larger than most snail species available for purchase. This is ideal for those looking for a good tank cleaner or just want an animal that’s easier to spot. 

Because they stay small, they only need about five gallons of tank space per snail. This is great for hobbyists that like smaller tanks because not many organisms can survive in just five to ten gallons of water.

Although mystery snails stay small in general, some mystery snails can be bigger than others:

  • Pomacea bridgesii are the rarer species of mystery snail and can get quite large. Snails of this variety have been found up to 65mm in height. 
  • Pomacea diffusa stay on the smaller side and are better suited for life in an aquarium. They only reach about 40mm in width and 45mm in height. 

How Fast Do Mystery Snails Grow?

Many mystery snails are full grown when purchased in-store. However, if you are lucky enough to find a juvenile during your search, you’ll be in for a treat!

How fast do mystery snails grow? One of the things that makes these snails so exciting is how fast they grow — it almost seems as if they are growing before your eyes. 

Mystery snails eat constantly, and they will eat just about anything. If they are kept fat and happy, they will grow very quickly. In fact, mystery snails can double in size in just a few weeks. 

If you decide to allow your snails to breed, you will see just how quickly these snails can grow from egg to adult. The entire process only takes about eight weeks total, and they can potentially reach their full size within that time. 

How Long Do Mystery Snails Live?

So, now that you know what kinds of mystery snails there are and how big they might get, you might have some other questions. How long do mystery snails live? That’s one of the most important things to know when purchasing any new pet. 

Mystery snails usually live for about a year, so you shouldn’t worry if your snail dies a few months after purchasing them. They may have been older to begin with, and it doesn’t necessarily mean that you weren’t giving them proper care. 

However, they will thrive and may live longer when cared for properly. Even if their caretaker has given them the best care possible, they likely won’t make it past one year. Still, some aquarium keepers have reported mystery snails living up to four to five years, but this is rare. 

How To Care For Mystery Snails

For people who have never had snails before, they might be wondering, “how do you go about caring for mystery snails?” Fortunately, they are pretty simple and mainly fend for themselves. 

Feeding Your Snails

Your new snails are very easy to feed because they like to feast on natural organic matter such as leftover food and algae. Because of this, they will most often be found roaming the substrate at the bottom of the tank looking for their next meal. 

They play an important role in the aquarium by eating what your fish leave over. By getting rid of the organic matter trapped in the substrate, mystery snails keep the water conditions healthy and help trapped nutrients return to the water column. 

Mystery snails also love feasting on greens like aquarium plants, kale, and spinach. Keep in mind that if you feed them fresh veggies, do so in small amounts. Anything that is not eaten quickly will degrade and dirty up the tank.

Aquariums that are new may not have accumulated enough organic matter to keep your snails alive. In this case, you can purchase algae wafers that sink to the bottom of the tank and make a good meal for the hungry critters.

To know more about what mystery snails eat, read our full article here.

Keeping A Healthy Tank

how big do mystery snails get

How to take care of mystery snails is really simple, but they need a stable environment to thrive. Water parameters should be constant. It can be hard to remember what your water parameters should look like on a daily basis, so consult this table for reference:

0ppm0ppm<40ppm7.6-8.468℉-84℉kH 12-18

*Keeping the pH within the designated range is especially important because a lower pH can degrade the snail’s shell.

Anything outside these standards can prove fatal to your snails and to any other organisms in your tank. It is important to keep in mind that the preferred pH, water hardness, and temperature varies between organisms, so always do your research for compatibility before adding tank mates. 

If you’ve never had an aquarium before, you may be wondering how to make sure the water stays healthy. 

Firstly, before adding any organisms to your aquarium, you want to let your tank cycle for about two months. Letting the aquarium cycle ensures that beneficial bacteria can grow and congregate in your tank. 

Don’t worry, bacteria isn’t a bad thing to have in your tank. Quite the opposite, actually, because they break down harmful ammonia and nitrites to make the water safe for your fish and snails. Once your tank is established and there have been organisms residing there for a while, bacteria will not be enough to keep the aquarium clean. 

This is where a filter comes in. 

Watch this video:

Do Mystery Snails Need A Filter?

Filters are wonderful devices for keeping your aquarium clean. Just as the name suggests, they filter out any dirt or impurities in the water, helping to maintain ideal water parameters. 

Technically, because mystery snails are so hardy, they don’t need a filter to survive as long as the water conditions are good. However, if you are new to the aquarium hobby or have trouble maintaining water quality on your own, it is better to be safe and utilize a filter. 

Where To Buy Mystery Snails

Mystery snails are so common that you can usually find them at any pet store that sells fish. They are usually cheap as well, retailing for only a few dollars. 

You can purchase mystery snails from online retailers as well, even from places like eBay and Amazon. Those may not be the best option, though, and we recommend purchasing from a reputable aquarium dealer whether you choose to pick out your snails in-person or online. 


Whether you are new to the aquarium hobby or have been keeping tanks for years, mystery snails will always be one of the best additions to your aquarium. 

Small, colorful creatures, mystery snails are fun to watch and functional for your tank, cleaning up algae and debris. They are safe to keep with almost any kind of fish and do not take up a lot of space. 

Are you ready to add a new, entertaining critter to your freshwater aquarium? Choose a mystery snail and you’ll discover why it is no mystery they are so popular.

You can also read our full article to know what mystery snails eat, do mystery snails hibernate, do mystery snails eat algae, how mystery snails mate or read more guides to mystery snails and other kinds of snails here. Or you can find out how big assassin snails get here.

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Frank Kane

By Frank Kane

Frank is a huge animal lover with many pets of his own. He loves sharing all his knowledge of all creatures here and learning more whenever possible.