Cistern Cooler

[Fish Isla]

Has anyone here set up a water cooler pumping the cool water from a cistern through coils in there nutrient tank. I am just getting started with Hydroponics. I live in Mexico and on any given day my Nutrient tank is in the 90's. My Cistern in right under where I have my setup. I was thinking of pumping the cistern water through a coil in my nutrient tank if the system was closed to keep the cooling water clean I could just pump the water right back into the cistern.

[GardenState]

It would be geothermal cooling in a sense.
What is the average temp of the cistern? I'm sure there is a scientific way of figuring out how much coil you would need to chill the nute tank x numbers of degrees.
Depending on how many gallons your nute tank you might want to test a few things out. Drop a small pump into the cistern and run the water through a coil of say 25-50' feet of pipe and see how it works out. I say small pump because there is no need to move the water that fast. It can only exchange heat at a slow rate because there most likely is not a large difference in the water/nute temperature. Your cistern is what 65-70 degrees not 40.

[fintuckyfarms]

Last summer I used a cheap cooler and coiled tubing (with the nutes) through the ice water from my nutrient tank. It worked like a charm! I just unplugged the pump when the nutes got cool enough. It also added some air into the system as it dropped back into the nutes. I will probably start it again soon as the temp today will be above 100.