Nutrient uptake for plants ceases if the reservoir temperature is too high. The ideal temperature for a hydroponic reservoir is generally between 65 and 75 degrees farenheit. If you keep your roots cool you will reap large rewards later in fruit mass. Recirculating chillers are excellent at efficiently keeping even the largest of reservoirs cool. These chillers, if properly sized, can keep you cool even in the Hot San Joaquin Valley of California where we at A Higher Yield live.