Pond Snail Facts – Are Snails Good or Bad for Garden Ponds?
If you have a decorative pond, you’ve likely come across some resident snails and are wondering whether or not to keep them around. Before we delve into the specifics of these slimy little critters, let’s start with a bit of basic background. Pond snails are members of the gastropod family, along with mollusks, slugs, and approximately 60,000 other species. Oftentimes, they are introduced accidentally into ponds by discretely hitching a ride on aquatic plants, or will move in of their own accord from any nearby water systems such as rivers or wetlands. On occasion, they’ll hitchhike on the backs of turtles that have been sedentary for a while (or unintentionally on your dog or cat as they brush against a plant with snails or eggs on it), transferring to your pond if they find it suitable.
Much like amphibians, snails meet a portion of their oxygen needs by essentially breathing through their skin, though some species also have gills (yes, snails can have gills!) while others have a single, tiny lung-like organ and need to periodically surface to breath. Depending on the snails native to your region, some will be happy living permanently under the water, whereas others may need to visit the surface for a breath every now and again!
Do Pond Snails Eat Algae & Plants?
Depending moderately on the species, freshwater snails consume algae, leafy vegetation, dead fish and snails, and certain vegetables and fruits like carrots and apples. If you have a heavily planted pond, there should not be any major damage to plants as small amounts of snails won’t have much of an impact. They’ll also consume softer nuisance algae before they eat most plant foliage, so they’re useful for keeping algae in-check and will only go for plants if there is little else to eat. However, if you have only a lightly planted pond or little algae, you will need to keep snail reproduction in-check, as they’ll eventually grow too large in numbers for plants to recover after foliage is eaten.
Common Fresh Water Pond Snails (Europe or US Native Species)
1) Ramshorn Pond Snail (Planorbidae)
Named because their shell is shaped much like a ram’s horn, the ramshorn snail breaths air via a lung and through their skin. Because of this, they are able to thrive in environments with low dissolved oxygen levels compared to species with gills. They also prefer areas that are not overly clean, meaning that they have plenty of algae and vegetation for the snail to feed on, though these snails are found in clear, oxygenated waters as well. Fairly common, these snails are often considered a “pest” species, as they can reproduce quickly and lay a large number of eggs at a time. However, soft algae species are their favorite food, and so long as these are readily available they are unlikely to eat much of your pond vegetation and can help prevent algae overgrowth. They’re a very cheap, low bio-load, and safe choice for most fresh water ponds.
2) Great Pond Snail (Lymnaea stagnalis)
The great pond snail, or Lymnaea stagnalis, is a fairly widespread species occurring in the Holarctic regions of Europe as well as portions of Canada and Russia. As its name implies, it’s a fairly large snail whose shell can grow to be up to 7 centimeters in diameter. They prefer calm, still water with plenty of vegetation, or very slow moving rivers and streams. Their diet primarily consists of vegetation (both living and dead) and algae, but they will also consume insect larvae (like pesky water beetles), small newts and fish, and even other snails.
3) Wandering Pond Snail (Radix Balthica)
Found throughout much of Europe and north and west Asia, the wandering pond snail is fairly small at an average maximum size of 2.8 centimeters. While they inhabit a range of aquatic environments, they prefer eutrophic, still water bodies. Eutrophic ecosystems are considered unhealthy, and so finding this snail in your pond may give you cause to test your water quality to make sure nutrients aren’t overloaded and there is plenty of dissolved oxygen. They will feed on plant matter, decaying organic debris, and algae.
4) Big Ear Pond Snail (Radix Auricularia)
Native to Europe and East Asia, this species has also spread to the United States and New Zealand. They are capable of living in turbid waters, but generally prefer lentic lakes, ponds, bogs, or rivers. A large species, big ears can grow up to 6 or 7 centimeters in diameter. Much of their diet is composed of green algae species, decaying matter, and sand grains.
5) Dwarf Pond Snail (Galba Truncatula)
A dwarf species, lesser pond snails typically only grow to a maximum of 1 centimeter in diameter. Preferring very small, still bodies of water (including puddles!), it can be found across all of Europe, North Africa, portions of Asia, and Alaska. Like the other species talked about here, lesser pond snails will eat aquatic vegetation, algae, and decaying organic matter such as dead fish and leaves. They’re also sometimes referred to simply as lesser snails due to their small statue.
6) Other Snail Species (Non-native)
As well as the wild native species above, you may also hear about other snails, such as trapdoor snails, mystery snails, assassin snails, rabbit snails and tadpole snails. These species, among others, may be able to live in outdoor ponds if they’re not tropical (require higher temperatures), but you would also need to check they’re not an invasive species in your area. If your pond is close to natural water ways, trying to attract native species is recommended so non-native species don’t become invasive to the surrounding environment. Many of these types of snails are kept in aquariums or raised ponds, which ensures they’re more easily controlled and can’t readily escape.
Benefits of Having Pond Snails:
While some species are considered more desirable than others, in general pond snails can play an important role in your pond’s ecosystem by grazing on algae. They also aid in nutrient cycling by feeding on detritus and releasing nitrogen from sediment. Some freshwater snails, such as the great pond snail and the lesser pond snail, are more sensitive to pollution and can warn you if your pond isn’t healthy. If snails are suddenly coming to the surface of your pond, the water quality is likely poor. By contrast, if you find pollution-tolerant species like the wandering pond snail, this is also an indicator that your pond might be unhealthy and should be tested and monitored.
Drawbacks of Having Pond Snails:
Most pond snails do consume algae – however, many of them prefer the healthy, soft green algae that’s easier to scrape off rather than harmful blue-green algae, or cyanobacteria. In addition, most snails are hermaphrodites and reproduce quickly. If your pond becomes overpopulated, they may eat your pond plants and kill them over time, particularly if there is not enough algae. One way to mitigate this is to provide leafy vegetables. Another is to avoid having or remove any snails from the physa genus, such as the acute pond snail, as these species reproduce exceedingly quickly and gorge themselves on necessary healthy algae, as well as diatoms that are absolutely essential for aquatic life. On top of this, if snails are allowed to reproduce freely, they will hugely contribute to waste as they begin to die off. This can cause spikes in harmful waste substances, such as ammonia and nitrites, which are deadly to fish.
Furthermore, many wild snails are often hosts to various parasites that can pass to fish and mammals. If you decide to have snails in your ornamental pond, obtaining them from aquariums, fish farms, and breeders significantly lowers the likelihood of them hosting parasites or viruses. Never catch snails from a natural environment and introduce them to your pond, as they can host a range of pathogens, bacteria, and nasty parasites!
How to Control & Remove Pond Snails & Eggs
If you come across snails in your pond but don’t wish them to be there, there are a number of actions you can take to minimize their numbers or remove them altogether. Perhaps the most obvious solution is manual removal by hand, with a water vacuum, or nets. You can also introduce predators that eat snails, such as frogs or assassin snails. Assassin snails, as the name implies, eat snails smaller than themselves. They also require a male and female to mate, so they don’t reproduce nearly as quickly as other snail species, and only lay a few eggs at a time rather than many dozens. As an added bonus, they’re quite colorful and beautiful.
Another easy option is to form a sort of snail trap by placing a lettuce leaf on your pond’s surface and leaving it overnight. By the next day, there should be a significant colony of snails gathered on the leaf, which you can then remove from your pond. However, this won’t remove all of the snails in your pond, and will also attract snails that you may want to keep.
If these methods aren’t giving you the desired results, you can utilize various chemicals as a last resort. Keep in mind that these chemicals may impact other organisms in your pond as well if you don’t use the proper amount. The most common chemical is copper sulfate, which kills both slugs and snails on contact. However, it is very toxic to both plants and fish, so we cannot recommend it over other safer control methods.
To ensure that you keep snails under control, you should regularly clean out your filters and change the cartridges to remove any eggs and tiny juvenile snails. At least once a year, empty out your pond and thoroughly clean the liner, rocks, plants, and any decorations. The easiest way to do a large water change and clean-out is with a water vacuum with dual-flow function and sludge filter, as you can clean and filter water at the same time!
Pond Snails for Sale – Where to Buy Pond Snails?
Pond snails which are native to your region will eventually end up in your pond so long as there is plenty of food (algae/plants) and places for them to hide from predators. Since many native wild species are not popular in the aquatic trade, you’ll likely just have to remain patient if you’re looking for a specific native snail.
However, more popular ones such as trapdoor snails, mystery snails, assassin snails, and even some varieties of ramhorm can be found online from numerous online stores. Funnily enough, even Amazon has a very good stock of live pond snails as many breeders have switched to their store front in recent years. You can check the current selection of live species below: