We have a small Koi pond and like many people we always get string algae in the spring. It's not a big problem and we are able to treat it with a single chemical treatment in most cases. However for some reason this year we got it over the winter, we had a very cold winter here in Louisville I'm not sure how or why it decided to start then. The chemical treatment we use is not effective until the water is at least 50°, preferably higher so that's not an option. Does anybody idea have any idea of how to get rid of it in a pond that is still cold?