Actually dwarf puffers don't like frozen food in general because it doesn't move like it is alive. With good circulation in the tank it's much easier to make them think the freeze dried stuff is alive then frozen chunks. But this isn't about puffers...
You can always pre-soak the freeze dried stuff as it expands to full size in a matter of seconds once it hits water. And I've found some people that had really picky frogs that ended up only eating the freeze dried stuff. But there isn't anything wrong with frozen stuff either (especially since you've already got some handy

) and a lot of frog owners prefer it to everything else if their frogs will take it. Check out this page on the Frogs,
the second paragraph shows how this guy feeds his frogs. He says he just gives them a "pinch" every 3-4 days. I'm not sure how to give a pinch of a cube of blood worms though. I've heard of people using cheese graders/slicers to scrape off pieces of the frozen block, maybe give that a try?