Sorry about to both of you guys for your lost amphibians. When it comes to nutrition I always try to give a varied diet of different annelids and arthropods. Most of the time (true in human health/nutrition as well), giving straight vitamins such as a supplement (as in dusting crickets or a human taking a pill) does not absorb very well or not at all. The best method for vitamin absorption is through an animal (or person) consuming food. That's what is cool about nutrition and what needs further study, is how the interaction of certain food(s) allow for proper vitamin absorption.