Here is an idea. If you buy a hot tub air pump and plumb some pvc together with a horizontal pipe running about 10' along bottom of pool several holes drilled in it and an end cap you could cool the temp during the night possibly. I get this idea from a friend who has hooked up the same stuff to steel pipe running through his wood burning stove and the heated air then is blown into house with the hot tub pump which you can control the speed of.