Thanks for the advise Grif!
I've got an ID on the worms. It's Perionyx excavatus. They actually use it as composting worm and not for feeding. It has a sort of blue sheen under the white light.
Although they are sold as composting worms, are they safe to use on amphibians?
Thanks Locascio, I've been using Prime for quite some time too. But mainly for my fish tanks. Since it can double its function to be used for my frog as well, that is just perfect!