Ideal night temperatures

[MouseKilla]

Just wondering if anyone knows the ideal range for BCIs night temperatures. I heat the enclosure with a regular light bulb that gives off enough heat through the day. It is on for about 12 hours a day, 9am - 9pm. It eventually cools to room temperature at night then gradually heats up through the day. I've heard that the temp drop at night is beneficial so I'm more or less wondering if room temperature might be too low.