Hi! This is a good question. Redworms(also called compost worms or red wigglers) are smaller than nightcrawlers and seem like a good option, but they have a foul taste that (most) amphibians dislike. Many frogs will not eat ANY earthworms after trying to eat red wigglers. The nightcrawlers are great food for frogs(if a bit hard to eat sometimes). Some stores also carry mini nightcrawlers. If a worm is too big, you can cut it in half and feed half to the toad at a time. The one major thing is to get natural earthworms. Bait shops sometimes dye them, which you don't want your frog eating.