You can use a Habistat Day/Night Dimming Thermostat to replicate the day/night cycle your reptile would experience in the wild, within the comfort and safety of their vivarium or terrarium.
Some reptiles, especially nocturnal species such as Leopard Geckos are especially sensitive to the day and night cycle, becoming more active at night when they are less likely to be noticed by predators - not that they are likely to encounter any living with you!
However this behaviour is built in and instinctive after millennia of evolution, and so to make them happy, you are best off using a Thermostat with a night-time-drop like this Habistat Dimming thermostat.
While it functions like a standard dimming thermostat, allowing you to run up to 600ws of light emitting heating equipment and using a remote sensor to adjust the intensity to maintain the correct temperature, it also has the facility to use a timer or a Habistat 'Night eye' (not included in this purchase) to establish a night-time temperature for your thermostat to work towards.
Reliable and used by reptile keepers all over the UK and beyond, it is available from Swell Reptiles at the best price and with Next Working Day Delivery options.