[chairman]

I currently have four crested geckos, a ~15 year old female, her son (12), and two of her grandsons (9). I keep my geckos at around 70 in the winter and 76 in the summer; they do well at those temperatures.

The one really strong guideline for temperatures for crested geckos is to not let them get warmer than 80; sustained temperatures above that mark can cause neurological damage or death to geckos. You are correct that the general target temperature that you should be after is between 70 and 80.

That said, that it not the only way to keep crested geckos. You can keep them in enclosures with cool sides of 70 and a daytime basking spot that provides a surface temperature of around 85. Back when I bred crested geckos I kept my geckos in such a setup.

For your situation I would suggest only providing the additional heat source during the day. You could also use an under tank heater to raise temperature and humidity by heating water in a damp substrate.