I raised two Green Frogs from tadpoles and kept them for several years. I fed them mainly on algae tablets. Green Frog/Bullfrog/Leopard Frog tads are generally too big to be eaten. If they are small and black, then they're toadpoles. I have around ten billion of them in my fish pond right now, and the goldfish don't touch them--apparently they're toxic.
What kind of setup you'll need once they're grown up depends largely on what kind of frog/toad they'll be, if they live in the water, on land, or in trees. Mine I kept in a 25gal tank filled up about 1/3 of the way with pebbles as the substrate forming a small island on one side of the tank. Unlike many reptiles, frogs/toads do not need UV lighting to survive, but they do require liberal amounts of crickets, so be prepared for that.