Why Is My Snail Eating Its Shell? (& What To Do About It)

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On several occasions, I have observed my snail seemingly eating its own shell. Initially, I dismissed this behavior as a meaningless and infrequent incident.

Over the years, I came across several accounts of aquarists witnessing their snails engaging in the same behavior of apparently consuming their own shells.

Drawing from my experience and knowledge on this topic, I have compiled a comprehensive article that encompasses everything you need to know.

Let’s dive right into it.

A snail was caught nibbling on its own shell.

Why Is My Snail Eating Its Shell?

Snails might eat their shells as a result of inadequate calcium levels, a crucial nutrient required for shell formation and strength. Additionally, snails could resort to nibbling on their shells when experiencing stress, leading to unusual behaviors.

Snails cannot live without their shells. This is why snails that frequent the top scare people. They know that a snail can crack its shell when it falls from a great height.

Your biggest worry is the snail drying out. Additionally, shells are vital to the snail’s safety because they repel predators.[1]

Therefore, you can understand why a snail rasping on its shell would elicit concern. The following factors can explain this behavior.

1. The Snail Needs Calcium

Did you know that snails use calcium to make and strengthen their shells?

A paper in Plus One (Johel Chaves-Campos, Steven G. Johnson, Lyndon M. Coghill, Francisco J. Garcia de Leon) noted that snails supplement the organic compounds they synthesize with the organic compounds they ingest.[2]

In other words, the meals you feed a snail can influence the volume of calcium it has at its disposal when making and maintaining the shell.

Therefore, a calcium deficiency can compel snails to eat their shells. This sounds ridiculous until you realize that snail shells have a lot of calcium.

That is why a section in ‘New Trends Of Functional Materials For Wastewater Treatment Applications’ explored the role shells could play in wastewater treatment.

The study noted that low-cost sources of calcium are effective wastewater treatment tools. It also highlighted the high calcium content in shells.[3]

Therefore, if a snail has a calcium deficiency, it may turn to the shell, the closest source of calcium.

In the wild, creatures like turtles, shrews, and birds eat snails for their decent calcium content. Snails serve a significant purpose in the food chain.

Besides eating its shell, a snail that is experiencing calcium deficiencies may exhibit other symptoms, such as:

  • Visible pitting or erosion on the shell
  • Softer or thinner shell than usual
  • Unusual or uneven shell shapes
  • Reduced mobility and loss of appetite
Due to the high calcium content, snail shells are a source of nourishment for snails when their diet lacks sufficient calcium.

If you suspect that your tank doesn’t have enough calcium, here is how to fix this in a few simple steps:



  1. Test the calcium levels in your aquarium using an aquarium water test kit to determine the current calcium level.
  2. Shake the Kent Marine Concentrated Liquid Calcium bottle well before use.
  3. Use a clean measuring cup or container to measure out the recommended dosage of the calcium solution based on the size of your aquarium. Follow the manufacturer’s instructions for the appropriate dosage.
  4. Slowly pour the calcium solution into your aquarium, taking care not to add too much at once. You can pour the solution directly into the water, or add it to a high-flow area of the aquarium using an air stone or powerhead to help distribute the solution.
  5. After adding the calcium solution, test the calcium levels in your aquarium again after a few hours or the following day to ensure that the levels have increased to the desired level.
  6. If the calcium level is still too low, you may repeat the process with a slightly higher dosage of the calcium solution.

Pro Tip: The recommended calcium level in a snail tank is around 200-300 ppm (parts per million).

2. Your Snail Is Stressed

You can blame most abnormal behaviors in the tank on stress, especially aggressive tendencies.

This is why overcrowding is so dangerous. The aquatic creatures are more likely to attack one another.

Besides eating its shell, a stressed snail may present the following signs:

  • The snail becomes lethargic and spends most of its time motionless at the bottom of their tank.
  • Reduced feeding behavior and weight loss.
  • Stress can change shell color in aquatic snails, either darkening to black or losing color.
  • Some snails will dig and bury themselves in the substrate.

The following are the most common causes of stress among aquatic snails:

  • Poor water quality: high levels of ammonia, nitrite, nitrate, and other harmful substances in the water can stress and harm aquarium snails.
  • Fluctuations in water parameters: sudden changes in temperature, pH, and hardness can stress aquarium snails and make them more susceptible to disease.
  • Overcrowding: too many snails in a small aquarium can lead to competition for resources and space, causing stress.
  • Lack of hiding places: aquarium snails need places to hide and feel secure, and a lack of hiding places can cause stress.
  • Predators: other fish or invertebrates in the aquarium that prey on snails can cause stress and even death.

Once again, check the tank’s conditions and eliminate low-quality water as a potential culprit.

Many aquarists tackle erratic behavior by performing a water change because they know that poor water conditions cause stress.

If this behavior disappears after a water change, you can conclude that stress drove the snails to eat their shells.

When experiencing stress, certain snail species may bury themselves in the substrate.

3. Your Snail Didn’t Actually Eat Its Shell

What have you seen to reach that conclusion? Is your primary piece of evidence the thin layers and transparent edges?

Shells can deteriorate because of poor conditions. For instance, you need a neutral pH to maintain a shell’s strength.

Acidic elements weaken the calcium carbonate, which makes the shell brittle and more likely to break.[4]

Don’t blame the snail for the shell’s poor state until you test the water and eliminate acidic conditions as a potential culprit.

These are the ideal water conditions for the average aquatic snail:

  • Temperature: 20-28°C (68-82°F)
  • pH: 7.0-8.0
  • Ammonia: 0 ppm
  • Nitrate: < 20 ppm
  • Nitrite: 0 ppm
  • Water hardness: 5-15 dGH

Could It Be Normal For A Snail To Eat Its Own Shell?

Yes, this behavior could be normal.

The notion of a snail eating a shell is nothing new. Newly hatched snails will eat the casings of their eggs to consume the calcium.

Older snails will also eat the shells of their unhatched young ones to extract the calcium.[5]

If you have multiple snails in a tank, they may eat each other’s shells.

Some aquarists think this behavior is accidental, especially among snails with a significant size difference.

The smaller snails don’t realize that their larger counterparts are actually snails. They think the shells they discover are independent calcium sources.

However, snails have an acute sense of smell. They can detect the scent of another snail’s slime.[6]

In a garden, you will see the snails making full-body contact as they pet, vet, taste, and smell each other. This behavior can last hours.[7]

It suggests that snails can identify each other to an extent. But this doesn’t change the fact that snails eat the shells of other snails.

If a snail can eat a shell encasing another living snail, why wouldn’t that snail eat its own shell during moments of desperation?

This doesn’t mean every snail eating its shell should concern you. First of all, snails don’t do nearly as much damage to their shells as you think.

Snails have tiny teeth that hardly cause any damage.

The creatures have thousands of microscopic teeth (Radula). Those teeth are too small to bite in the traditional sense.[8]

Instead, they scrape their food. Sometimes, they bite a large piece off their food source. However, you shouldn’t expect them to pull large chunks out of their shells.

Secondly, snails use those microscopic teeth for grooming purposes.

They eliminate the rough edges, making the shell as smooth, clean, and comfortable as possible. This grooming technique is not a cause for concern. 

Can You Feed Snails EggShells Or Dead Snail Shells?

Feeding your snail with eggshells and dead snail shells is a perfectly normal and reasonable way to enhance the strength of its shell.

If your tank is well-maintained, but the snails are still eating their shells, you can give them more calcium-rich foods, including:

  • Eggshells
  • The shells of dead snails
  • Cuttlebone
  • Calcium supplements
There is an exceptional YouTube video demonstrating how to feed snails using eggshells.

You can also supplement their diets with the following:

  • Peas
  • Kale
  • Cucumber
  • Oats
  • Hibiscus
  • Lily
  • Strawberry
  • Cherries
  • Apples

Overfeeding isn’t a concern for snails. They will eat until they are full and then stop.

Again, snails won’t do significant damage to their shells. And any damage they do, they can fix.

Snails can repair mild cracks and even holes. You should only intervene with plaster and sticking tape when you notice severe breaks and tears.

Do Snails Eat Other Snail Shells?

If you own a snail tank, you know that snails eat the shells of other snails because you have given your snails the crushed shells of other snails to eat.

Moreover, some snails engage in shell-rasping behavior on the shells of other living snails, which can be mistakenly perceived as aggression or even mating behavior.


If you’re in a hurry, here’s a quick rundown of the key points mentioned above:

  • Snails need calcium for their shells, and a lack of it may cause them to eat their shells.
  • If the water has low calcium, it’s probable that your snail will display additional indications, such as noticeable pitting and erosions on the shell.
  • Stress can also lead to this behavior due to poor water quality, overcrowding, and predators.
  • If a snail exhibits unusual behavior, investigate potential causes and take necessary measures, such as supplementing calcium, improving water quality, and reducing stress.


  1. https://brill.com/view/journals/ctoz/88/3/article-p277_277.xml?language=en
  2. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0044374
  3. https://www.mdpi.com/1996-1944/16/3/1095
  4. https://www.ntlabs.co.uk/knowledge-hub/a-guide-to-apple-snails-in-the-aquarium/
  5. https://www.sciencefocus.com/nature/are-snails-born-with-their-shells/
  6. https://northernwoodlands.org/outside_story/article/snails-slime-is-sublime
  7. https://www.kqed.org/science/1446777/everything-you-never-wanted-to-know-about-snail-sex
  8. https://nhm.org/stories/microscopic-look-snail-jaws