If they're the glass worms I thinking they are,than yeah...they're probably too big. Mine won't even touch grindals until around 3-4 weeks. But,it can't hurt to try. It's amazing the size of worm they can eat once they start. If it's no more than twice as big as the fry I would at least give it a shot. You can always do a syphoning if they don't eat them.... or if one chokes and you panic.