Most Probiotic Ferments do best in a warm temperature setting. We recommend a temperature range from 74 F to 84 F (22-28.8 C) ,for Kombucha, Jun, Ginger Beer, Water Kefir, and Vinegar. While Villi and CSY and vegetable ferments like sauerkraut do well in the mid 60's (15.5 C) While one does not need constant temperature the greater the consistency the more reliable and predicable will be your ferment. OPTIONAL digital regulator helps maintain the optimal temperature without fear of over-heating.