Viviparus viviporous (Trapdoor Snail)
Trapdoor snails are very effective for cleaning the pond of algae they also help to breakdown organic matter.
These hardy snails feed at the bottom of the pond and they able to survive a winter in the UK. One snail per square foot of surface is a useful guide.
Molluscs eat algae and improve water quality, helping to preserve the natural balance of the pond.