We get cold temperatures and plenty of frost but rarely does the pond freeze over. That is good to know though that water heist and would be killed by the pond freezing. I currently have four water lilies and some cattails. The water will get very clear at times if we have not had rain, however there is a lot of algae and what I believe is American pond weed. I think I may go for trying to grow some water hyacinth in a tub or kitty swimming pool in the pond. OR does anybody else have other suggestions on plants that would do a good job of pulling nutrients out of the pond? I'm upgrading my aerator soon and using good bacteria to try to break down some of the muck. I've been informed by neighbors that my pond is at least 60 years old and was never taken care of until I moved in a few years ago.