Thanks Bill. In my personal pond, I typically come out of winter with low water, and even if the water was high, I usually have super clear water until the end of April or middle of May. So, my thought was that the medium or large varieties (if cold tolerant) would be a good choice. I had some of the shorter varieties, but they didn't grow taller when the water levels rose. Now to research where to get some that are NOT tropical varieties.