To feed worms I grab them with tweezers from bin, dunk them in dechlorinated water to rinse, pat dry on paper towels, and dust them if needed. Even when dusted, whole worms that are dropped in front of my frogs get grabbed within seconds. If you see a worm digging itself, it's easy to grab with feeding tweezers and pull out of substrate.
You can try to find smaller red wriggler worms (can get them at Petco or for larger cultures online) or cut the larger Night Crawlers into mouth width pieces. Cut as required (up to half) from worm's pointy end. Worm will heal until you use other half. How big are your frogs (SVL)? My 1.5 in. Pacman would eat a smaller 3-4 in. Night Crawler without problems. Now Fresita is 2.5 in. and can handle a larger 4-5 in. worm easy. Good luck

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