I don't think worms will be a problem for toads, I have woodhouse's Toads and they love anything I give them. Crickets, roaches, meal worms and earthworms. These days I have a colony of isopods(pillbugs), and they adapted to eating them instead of crickets very easily, in my experience toads are very eager eaters. Don't know about fowlers/American, but I think they're pretty similar from what I've read. I could be wrong, but I think if you wiggle it over them they'll go for it.