Here's a helpful guide: http://www.exo-terra.com/en/explore/uv_rating_index.php

I kept fire bellied toads before and since putting them on UVB you could see the results, they were more active, brighter and just healthier in general. I would use a 5% UVB above most set ups and supplement them with something like Repashy superfoods calcium plus LoD, myself.