I usually do cover my pool, however, last fall my cover came off (with a little help from my two golden retrievers, but that is another story!) around the beginning of November. Since the bulk of the leaves had already fallen, I decided to just leave it uncovered the rest of the winter. My water remained clear and pretty clean. Here in south-central WV, my pool doesn't get much ice. Occasionally a glaze, but not a frozen pool by any means.