Makes me wonder on how well bringing up the borate level would work when shutting down the pool for the winter. Usually I close as late as possible, mid-October and open early in April, so that the water is clear. But, sometimes there are warm spells or I open a bit later (this year!) and can get some green algae action. Seems like the borates may help, though I wonder how they would make out through 5-6 months of frozen water.