Greater Pond Snail (Lymnaea stagnalis)

Choose the greater pond snail for a planted pond

The greater pond snail (Lymnaea stagnalis), also called the great pond snail, is the largest pond snail in Britain. Its tall, pointed brown shell can reach 6 cm, and it spends its life grazing algae, soft water plants and the debris that collects in still water. For a garden pond, a wildlife pond or an unheated indoor tank, it is a hardy native grazer that stays active through the whole year.

Linnaeus named it Helix stagnalis in 1758, and it now belongs to the family Lymnaeidae. The species name points to its liking for still, stagnant water, as NatureSpot explains. It lives across the temperate zones of North America, Europe and Asia, reaching northern Norway and, in Central Europe, mountain waters up to 1,700 m, according to the Wikipedia species account. NatureSpot describes it as common and widespread in England but scarce in Scotland and Wales, and the IUCN Red List assesses it as Least Concern.

Check that it suits your water before you order

Know exactly what you receive

Choose 1, 2, 5 or 10 snails from the pack menu; the pack size is the number of live greater pond snails we send. Packs are sold by number rather than by shell size, so shell sizes can vary within a pack. Our photographs show the species; each shell differs a little in shade and markings. Please read our delivery page before ordering, especially during very hot or freezing weather.

Identify it in the hand

The similar wandering snail (Radix) is much smaller: Wikipedia gives adults of the related Radix peregra as 12–20 mm high. The research review by Fodor and colleagues (2020) gives greater pond snail shells of up to 55 mm, so treat 45–60 mm as the normal adult range and 70 mm as exceptional.

Plan for a 45–60 mm snail with a big appetite

This is a large snail with an appetite to match, and water plants are part of its natural diet. In a pond, volume matters less than plant cover: a well-planted pond produces enough algae, biofilm and dead leaves to keep a colony grazing without touching the healthy plants too much.

No care sheet gives a minimum volume for this species. Wikipedia notes simply that it is kept at room temperature in freshwater aquariums. If you keep it indoors, choose an unheated tank large enough to hold a good mass of robust plants, and use our volume calculator to check the litres of a rectangular tank or pond.

Use a three-step space check

1. Count the plants: the more vigorous growth, the more grazing there is to share.
2. Find the shallows: Fodor and colleagues describe shallow, vegetated water as its home.
3. Start small: it breeds from spring to late autumn, so a few snails soon become many.

Give it still, shallow, planted water

Fodor and colleagues describe its habitat as stagnant and slowly running shallow waters rich in vegetation; NatureSpot says the same, still or slow-moving water with plenty of aquatic plants. Wikipedia adds that in Germany's saprobic system, which grades rivers by how much organic pollution they carry, the species scores 1.9, indicating water-quality class II, the second-best class. In other words, it favours reasonably clean water and is not a sign that a pond can be left to stagnate.

The OATA pond care sheet recommends live plants for oxygen, pollutant removal and food; shallow ledges for a wider range of plants; enough sun without overheating; and an autumn net under trees. That is exactly the pond a greater pond snail does best in.

Divide the pond by function

Indoors, fit a lid: the OATA snail and shrimp care sheet recommends a cover to stop snails escaping.

Match the water: cool, hard and clean

No care sheet publishes exact water chemistry for this species, so the table sets OATA's pond targets beside what the species sources say:

OATA's figures are written for pond fish, but they describe the water the snails share, so a pond that meets them suits both. UK tap water ranges from soft to very hard by region, and rainwater top-ups are soft, so check your hardness with a test kit or our water matcher tool; in very soft water, cuttlebone adds calcium, as Wikipedia suggests for ramshorn snails kept in low-calcium water. Always treat tap water with a conditioner that removes chlorine or chloramine, as OATA advises. Our guide to pH and hardness explains the readings.

Watch how it breathes

Fodor and colleagues explain that in well-oxygenated water the greater pond snail takes in oxygen through its skin, and that when dissolved oxygen drops it breathes air through a lung, opening a small breathing hole (the pneumostome) at the surface. Snails that spend a lot of time hanging at the surface can therefore be a clue that oxygen is low: run the pump or fountain and clear rotting leaves.

Maintain the pond through the year

OATA recommends a filter for any pond holding fish, a pump or fountain to circulate and oxygenate the water, and weekly tests for ammonia, nitrite, nitrate, pH and hardness while a pond is new. Rinse filter media lightly in pond water removed during a partial water change, never under the tap, and replace UV lamps as the maker advises, normally every year. Before winter, OATA advises removing dead plants and leaves and trimming back marginal plants, because rotting vegetation can release toxic gases.

Follow a seasonal routine

Feed it algae, leaves and leftovers

Fodor and colleagues describe greater pond snails as mainly herbivores that prefer algae, water plants and detritus. Wikipedia lists what keepers feed them indoors: vegetables, salad, cabbage, fallen maple or oak leaves, cucumber slices, dandelion leaves, fish food and algae, and notes that they also eat Hydra viridissima polyps and other snails' eggs. Because water plants are part of its natural diet, the surest way to protect your favourite plants is to keep the snails supplied with algae, dead leaves and the odd vegetable.

OATA's care sheet for snails and shrimp suggests feeding two or three times a week, leaving pellets or wafers for at least 30 minutes and avoiding overfeeding. In a mature, planted pond, the snails find most of their food themselves; in a new pond or an indoor tank they will need these extra meals.

Build one measured meal

1. Choose: a lettuce or cabbage leaf, a slice of cucumber, a few fallen oak leaves or a sinking wafer.
2. Place: put it on a shallow ledge or the tank floor where the snails graze.
3. Wait: leave wafers for at least 30 minutes, as OATA suggests; leaves and vegetables can stay overnight.
4. Clear: remove anything left the next day so it does not foul the water.

Introduce new snails slowly

OATA warns that snails are very sensitive to copper and die if exposed even to low levels, so check every treatment and plant product first. Test for ammonia and nitrite, which OATA says must read zero before new stock goes in. Then use OATA's floating-bag method: float the sealed bag for about 10 minutes to match temperatures, add small amounts of pond or tank water over at least 30 minutes, and move the snails across by hand or net with as little bag water as possible. OATA's Plant Wise advice is to pour waste water onto the lawn or onto plants away from ponds and drains. Our step-by-step acclimatisation guide covers the same steps for fish.

Use first-week checkpoints

Choose pond mates with care

The greater pond snail does not harm fish. It does compete with other snails: Wikipedia notes that it eats other snails' eggs, so in a pond with several snail species it will reduce the others' spawn. Fodor and colleagues list leeches, crayfish and fish among its predators, so expect some losses of young snails in a fish pond and give them dense plants to hide in.

OATA's pond care sheet covers goldfish, rudd, tench, orfe, koi and sturgeon; it recommends at least 4,500 litres for koi, tench and orfe, while goldfish and rudd suit smaller ponds.

Ask five questions before mixing

1. Do the water ranges overlap? Pond fish and native snails share OATA's 4–24°C range.
2. Is there cover? Dense plants protect young snails from fish.
3. Does anything eat snails? Leave out crayfish and assassin snails.
4. Do you keep other snails? Expect it to eat some of their eggs.
5. Is any treatment copper-based? Read every label first.

Our tank mates checker helps with indoor mixes, and the assassin snail guide explains why that species belongs only in tanks without wanted snails. For pond fish, browse goldfish and coldwater fish, the Other Pond Fish category and our comet goldfish guide. Our aquarium Ramshorn Snail is a tropical species and should stay indoors, away from ponds.

Watch shells, behaviour and water

OATA's invertebrate care sheet lists the changes to watch for: unusual activity, colour turning darker or paler, more time spent in oxygen-rich areas, damage to the shell, growths or lesions, and a reduced appetite.

Pair each observation with an action

Wild snails carry parasites. Fodor and colleagues note that this species is an intermediate host of flatworms, including those behind liver fluke disease and swimmer's itch in people. OATA's 2020 recommendations warn that imported snails could bring parasites and diseases not present in the UK, which is why UK-sourced stock matters. Wash your hands after pond work and never move snails from wild water into your pond.

Expect eggs and manage the numbers

Each greater pond snail is a simultaneous hermaphrodite, carrying working male and female organs at the same time. Fodor and colleagues explain that in each mating one snail acts as male and the other as female, that sperm can be stored for two months, and that although eggs are normally fertilised by a partner, self-fertilising snails show little or no loss of fitness. In laboratory conditions an adult lays 2–3 egg masses a week with 100–150 eggs in each; the eggs hatch in 11–12 days, usually over 90% of them. Males mature at about 30 days and females at about 60, so snails can breed at two months old. They live for over a year in the wild and up to two years in the laboratory.

Control numbers without chemicals

1. Look: check leaves, stones and the pond liner for long, clear jelly masses.
2. Lift: remove surplus egg masses with the leaf or scrape them into the compost.
3. Feed fish less: OATA advises feeding only what fish eat in a few minutes, and leftovers feed snails too.
4. Rehome: pass surplus snails to another pond keeper rather than releasing them.

Meet a famous laboratory snail

The greater pond snail is one of the best-studied snails in science. Fodor and colleagues describe its use in neuroscience since the 1970s, from molecular signalling to behaviour, and in research on parasites, pollution, evolution and genetics; one breeding colony at the Vrije Universiteit in Amsterdam has been kept going for over 50 years. Wikipedia notes that its central nervous system has about 20,000 nerve cells, some up to about 100 µm across, large enough to study one by one. The same toughness that suits a laboratory makes it an easy snail for a garden pond.

Keep native snails in the garden

In January 2020 OATA asked the UK trade to source five native snails and mussels for outdoor ponds from UK stock only. It lists Lymnaea stagnalis (great pond snail) as native to the UK and explains why: imported animals could carry parasites, diseases or invasive hitch-hikers; snails can make their way out of ponds and be moved by birds; and imported stock may differ genetically from British populations. The same document asks retailers not to sell tropical aquarium snails for outdoor ponds.

Follow the three Keep It In rules

1. Never release snails, plants or water into the wild; OATA says released animals can harm native wildlife.
2. Keep species in their place: native pond snails outdoors or in unheated tanks; tropical snails indoors.
3. Dispose of waste carefully: pond water and plant trimmings go on the garden or compost, away from drains and natural water.

For more snails, browse our pond and aquarium snails and the full Molluscs category.

Answer greater pond snail buying questions

Is the greater pond snail the same as the great pond snail?

Yes. Both names refer to Lymnaea stagnalis, the largest pond snail in Britain.

How big does it grow?

Adults are usually 45–60 mm high and 20–30 mm wide; Wikipedia records rare shells of 70 mm.

Will it eat my pond plants?

It can. Fodor and colleagues list water plants alongside algae and detritus as its preferred foods, so keep plenty of vigorous plants and offer leaves or vegetables if soft plants are being grazed.

Can it survive a UK winter outdoors?

Yes. It is native to the UK and stays active all year, even under ice. Keep part of the surface ice-free, as OATA recommends.

Can I keep it in an indoor tank?

Yes, in an unheated tank at room temperature with robust plants and a lid. It is not a snail for a heated tropical tank.

Will it breed in my pond?

Almost certainly. It breeds from spring to late autumn, and in the laboratory lays 2–3 egg masses of 100–150 eggs a week.

Can I keep it with ramshorn pond snails?

Yes, but it eats other snails' eggs, so it will hold down the ramshorns' numbers.

Why does it keep coming to the surface?

It breathes air through a lung when oxygen in the water is low. Frequent surfacing can mean the pond needs more aeration.

Consult the care references

• Wikipedia: Lymnaea stagnalis: range, shell size and whorls, saprobic value, aquarium diet, nervous system, similar Radix size and IUCN status.
• NatureSpot: Great Pond Snail: shell size and colour, habitat, egg masses and UK status.
• Fodor I, Hussein AAA, Benjamin PR, Koene JM, Pirger Z (2020). The unlimited potential of the great pond snail, Lymnaea stagnalis. eLife 9: e56962: habitat, diet, breathing, breeding, maturity, lifespan, predators, parasites and research use.
• OATA: Recommendations on the trade in molluscs for use in outdoor ponds (2020): native status, UK sourcing and biosecurity.
• OATA: How to look after pond fish: pond water targets, testing, filtration, seasonal care, pond sizes and the floating-bag method.
• OATA: How to look after freshwater shrimp and snails: copper warning, feeding, acclimatisation time, lids and health signs.
• OATA: How to be Plant Wise: never releasing pond life and disposing of waste water.