These Are Hardy Snails, Able To Survive A Winter In The Uk. One Snail Per Square Foot Of Surface Is A Useful Guide. Molluscs Eat Algae & Add Oxygen, Helping To Preserve The Natural Balance Of The Pond.in This Collection You Will Receive:planorbarius Corneus (ramshorn Snails) X5 - a Large Freshwater Snail With A Coiled Shell.viviparus Viviporous (trapdoor Snail) X5 - very Effective For Cleaning The Pond Of Algae.one bunch Each Of The Oxygenating Weeds Listed - ceratophyllum Demersum, Fontinalis Antipyretica And myriophyllum Spicatum.