I use ZooMed Repti Calcium WITHOUT D3 2-3 time a week mixed 2:1 with ground bee pollen.*
Twice monthly I swap out the calcium mix with Repashy Calcium Plus LoD very lightly ~ every 2 weeks.
*bee pollen is optional it is unclear whether they can digest it at all or if it is simply roughage.
I don't have a concrete answer for that. Mine come on an hour after the UVB and then on for short periods thru the day and off an hour before the UVB. I use it less in summer and more in winter. It is off during any mistings.