There are absolutely no problems with feeding fruit flies. They are very easy to culture and maintain. The only drawback to feeding to larger frogs is that they are small and you will need a lot. I have my cultures for one year at a time before I start again with a new bloodline. Do as Kurt mentioned and DO NOT FEED WC INSECTS. Is it really worth the health of your animals when you can so easily culture your own food? It is horribly bad husbandry to take a chance like that, IMO. They depend on you so do the right thing.