We are now going to the simpler method Materials 3 gal rubber dish battery aerator plastic plate (floats on top and keeps it reasonably fresh) Budget $30 or less The goal of this is for winter storms during a blackout. Something that if I forget about it's fine and only worry about every 24 hours. Typically blackouts are 2 days and not very many happen. The lowest temp it has to withstand is 10 degree F and my yard is all shade. I prefer the nipple system but budget doesn't allow to get deep cycle battery and power inverter. I would prefer a battery heater but I can't find any with a reasonable price and run time.