I'm going to be using a mercury vapor bulb for my Sulcata now, and was wondering if it would be ok to have it on for about 8 hours/day and supplement its diet with vitamin d3 (in the calcium powder)? I know the recommended photo period is around 12 hours/day with a uvb bulb, but what if I cut it back and supplement the d3 in its diet? What symptoms/illnesses can occur from too much d3? As far as daylight, its in a sun room (windowed), so it has natural light all day (minus the uvb which is blocked).