It doesn't matter all that much. Bass can usually be kept in a tank kept at ambient temperature- no heater, no chiller. Anything from the 50s to the low 80s should be all right, though lower-temperature tanks are easier to maintain (fish metabolism is slower at low temps, so they eat less, poop less, fight less, etc.). Oxygen can also be a problem in warm (high 70s and up) tanks, as the fish need more but the water can hold less. Largemouth and Florida bass are the most tolerant of warm, low-oxygen water; smallmouth, spotted, and other black bass, as well as yellow, white, rock, and other bass prefer somewhat cooler and more oxygenated water.