Here’s why you never buy pond snails and what they do in your water garden.
To begin with, never buy them
There are enough hitchhikers on every bit of pond plant that you purchase that you do not need to actually purchase them. They will come to the pond seemingly on their own.
And what are snails good for?
Pond snails are the scavengers of the pond. They eat all manner of decaying vegetation and dead “stuff”. They are a necessary part of the natural pond.
For the most part, outdoor ponds do not share the concern of the indoor aquarium about controlling snails.
Indoor aquariums are under different kinds of growing conditions and snails can quickly get out of hand and consume tender plants. My experience in the outdoor pond is that yes, you will lose some vegetation to snails but the high levels of sunlight outdoors usually mean that the leaves regenerate very quickly. Also, fish in the outdoor pond will nibble away at the snails (especially if you don’t feed the fish – I seldom fed my pond fish) and help keep them under control.
And yes, they will chew up waterlily leaves something fierce – often towards the end of the season this gets worse. I tend to ignore them unless they’re defoliating the plants. A healthy lily will throw up lots of new leaves if it’s well fed.
What kind of pond snails are you likely to import into your pond when purchasing plants.
Malaysian trumpet snail. This small (2cm) long perfectly cone shaped snail comes along for the ride in almost all oxygenating plants. It never really seems to do much damage to plants even though it reproduces quickly (livebearing snail) and there will be quite a few of them by the end of the summer. They burrow into the soil during the day and come out to feed at night.
Ramshorn snails come in various sizes and the shell looks just like a ram’s horn (funny how the name and the shell are similar) The smaller varieties do not seem to eat too much but the bigger they come, the more damage they do.
Columbian ramshorn snails are often for sale in pond shops – this is the one that has a bright stripe along the length of the curve of the shell. The curved stripe is quite attractive but this snail can grow to 2 inches in diameter and leaves are one of its favourite foods. The snail is also very prolific. How’s that for a word to the wise. Avoid snails that have lots of babies and like to eat plants even if they are cute.
What we refer to as “pond snails” are a mixed bag of snail species.
Generally, you can’t avoid them in the pond and the trick is just to let them do their thing.
Naturalists suggest we not purchase pond snails and not encourage foreign snails to breed and enter our ecology. The problems with invasive plants are just as severe with invasive molluscs like snails.