I am finding out that slow, steady, and spread out is what keeps the water open while using minimal energy. I am using a 9" membrane diffuser with a larger hole pattern and having good results. I have not calculated or measured the CFM's but I bet they are less than 1.
I did a start up test with 3" of pretty good clear ice. I did auger holes so I'm sure that accelerated the opening of the hole. But 2hrs of run time in 3' of water the hole size was 8-10' diameter (approximate of course. Next time I will get my neighbor to swim out with a tape measure
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Extreme cold vs. pump life
