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.