Lights will add some heat to the vivarium during the day, and although a low of 65 at night to a high of 80 during the day is recommended, the terrarium will maintain a bit more heat over night than the room does, especially if it has a false bottom with water I don't know about all species, but the auratus and the tincs can stand down to 55 at night. It will take them awhile to warm up and move in the mornings, though. I think it was a Swedish breeder that told me his auratus regularly get down to 55 in winter with no permanent damage. I'd be more cautious with the thumbnails and pumilios, in particular, though.
I have found that my P. terribilis are far more susceptible to heat than cooling below 65 degrees.
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Patty
Pahsimeroi, Idaho
4 D. auratus blue
5 D. galactonotus pumpkin orange splash back
7 D. imitator
6 D. leucomelas
4 D. pumilio Bastimentos
4 D. fantasticus
6 P. terribilis mint and organe
4 D. reticulatus
4 D. castaneoticus
2 D. azureus
4 P vittatus
2 P. lugubris