Bettas are tropical fish from the warm waters of Southeast Asia. The optimal temperature for bettas is between 78-80° degrees Fahrenheit (25.5-27° C). Maintaining stable temperatures is essential for a betta's health. Sudden temperature fluctuations can lead to shock. Low temperatures prevent proper digestion and may lead to bloating or constipation. Hot temperatures increase a betta's metabolism and cause premature aging. Temperatures higher than 84° degrees Fahrenheit (28.9° C) can kill your betta.