leopard geckos, supplements and UV

I was just about to buy some multivitamins for my recently aquired leopard geckos and after a bit of research I have come to the conclusion that most people use nutrobal for both adults and juveniles. I see that you recommend arkvits for adults and nutrobal for juveniles.
I would like to hear what you recommend when it comes to calcium intake for an adult male leopard gecko, adult fertile female and  juvenile respectively. As I previously mentioned a lot of people seem to be using either nutrobal at every feeding, or nutrobal once or twice a week and then calcium powder for all other feedings.

Broadly, we recommend Nutrobal for juveniles and Arkvits for adults, used alternate feeding days, and CalciDust on the other days. We recommend a supplement every day so that they expect to eat white crickets, rather than the less dusty brown ones.

It isn't calcium which is the problem, without vit D the calcium goes in one end and out of the other. Vit D is very important, and in leopard geckos because they are nocturnal there is a question mark over the amount of UV you should provide. Excess UV in all species is a problem and can cause metastatic calcification issues, it simply isn't needed for nocturnal species such as leopard geckos which would barely be exposed to it in the wild. The problem is that its completely unregulated, people use a variety of UV sources, some of which are toxic etc. Some also use other Vit D sources.

Should I use lights which provide some UV for Leopard geckos?

This is a difficult question to answer. Leopard geckos like a number of reptile species are nocturnal. They rely on dietary sources of vitamin D3 BUT they are very efficient at converting D2 to D3 in the low levels of UV light at dawn and dusk. This gives them the ability to cope if the diet isn't optimal.
You could say they don't 'need' UV light but used cautiously it isn't going to do any harm to provide it.