i was thinking of using rheostats for night time heat source so the cage doesn't get to hot but i still get the light for viewing

anyone have any advice on what temp and where i should place the probe at. should i go by ambient temp or direct basking spot

i have my thermostats on order so im waiting of them. and im gonna need some help with were to place them too.

right now i get a ambient temp of almost 90 during the day with a out rages hot spot so im alway turning off the basking light on and off through out the day and if i go anywhere i just turn the lights off so it doesn't get to hot while im gone

any suggestions