If you use a bulb made for night use (black or red reptile bulb) or a ceramic heat emmiter, you can leave it on all the time. I would not leave a visible light on 24 hours a day. If you want to use a visible light during the day, I would suggest to get a timer for the lamp and a heat pad for under the tank. If you choose light wattages carefully, and make sure the heat pad is an ok temp, you can leave the heat pad on all the time, and use the lamp during the day to give a slight boost in temperature. Or you could get rid of the light entirely, and just rely on a heat pad. If you live in a dry climate, the latter might be the best option (lamps are drying).
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-audri
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