5.0 max on the uv as their skin is sensitive. Yes to lightning for day/night cycle & depending on where you're located, heating is an option, though this time of time prob not.
As above, low level UV is needed connected to a timer giving day night cycle, mine are inside so I only heat the water (using a aquarium heater) the ambient temp never gets to low as the combined effect of the heated water and my heated house keep the cold at bay.