Pond Snails 101: A Likely Sign of a Healthy Pond

Let’s Talk About Pond Snails: 

The Japanese Trapdoor Snails, also known as Viviparis malleatus. Snails are invertebrates in the gastropod family. They are herbivores that feed on algae and other organic debris. Japanese Trapdoor Snails were named because of their hinged fingernail-like plate that closes off the shell’s opening, which helps protect the snail from drought and predators. These snails are a dark color and vary in size. However, they typically arrive at your door at the size of a dime. These snails are cold-weather tolerant, which makes them a great addition to most water gardens.


For these snails to have a positive influence on your water garden, it’s recommended to have a group (escargatoire) of at least 10 snails per 50 square feet of water. Farm ponds or bigger water features will require at least 200 snails to have a positive effect. These snails will reproduce naturally a few times throughout the year. They have 3 to 5 live young per birthing, boosting the population in your water garden without overpopulating like egg-bearing snails do.

Male vs Female

There are male and female Japanese Trapdoor Snails, so how can you tell whether to name them Jack or Jill? Simply get a peek at their antennae. Antennae on females are the same size, and males will have one antenna that is shorter than the other. The shorter antenna doubles as a reproductive organ.

New Digs

After their travels, your snails will require a little time to adapt to their new home. Like fish, it is good to acclimate them slowly, particularly in chilly early-season waters. Put some pond water in the bag and float them in the water for a few minutes, making sure to keep them out of the direct sunlight. Once they are acclimated, leave them in a shallow part of the water. Allow them to work their way over to the deeper parts of the water. If you notice some of the are floating, fear not; air can sometimes get trapped in the shell. As long as the trapdoor is still intact, your snails are alive, and the trapped air will work its way out.

Home Sweet Home

Snails take their homes with them on their backs. If they sense threat, they can hideout inside their shells away from potential danger. They feed on algae, leaves, excess fish food, and other decaying matter when they get hungry. Like other aquatic critters, your snails require oxygen to survive. An aeration system will keep the oxygen flowing, so your gastropods, and all other aquatic life, stay happy and healthy.

Tougher than your Average Pond Snail

Japanese Trapdoor Snails are tough little guys and can handle temperatures down to 0°F. Japanese Trapdoor Snails get their oxygen from the water using their gills, unlike other snails that use their version of a snorkel to get oxygen from outside of the water. This allows them to stay warmer at the bottom of the pond instead of coming up to the cold surface during the chilly winter months. Like fish and aquatic plants, snails will not survive if the pond freezes over. Typically, depths of 20” to 30” provide a safe haven for aquatic life.

Hide and Seek

There will be times where it seems that your snails have disappeared, particularly in the spring and summer months when the water gets warm. Snails hide in the rocks, gravel, and plants in their habitat. Even though it can be annoying when they go incognito, fear not! They will continue to work hard, feeding on algae and keeping your pond clean. If you have the need to see them, you can try setting a lettuce leaf in your pond. Check on them in a few hours, and your gastropods should gather around the lettuce.

Word of Caution

Most algaecides can kill these invertebrates. It’s important to read any precautions and instructions on a chemical prior to using it to treat your pond. The most effective way to keep your snails, fish, and water healthy is to manage your pond proactively.