This is my second year with my pond. I have a very large amount of some unknown variety of snail. They are in the skimmer, filter, stream, waterfall, everywhere. They eat all the algae and the pond looks awesome. As a treat for the fish, I scoop up a bunch and crush the shells and throw them back into the pond. The fish (gold) go nuts eating them. My water is great and everything looks awesome. Colder nights taking there toll on hyacinths and lily, though. Anybody else do this and is it OK to do?