Collecting real-world answers here. Tell us:
1. What your ducks will do almost anything for.
2. Anything you've been told never to feed them (and, if you know, why).
3. What your main feed is, and your ducks' ages — feeding needs change over a duck's life.
Please say where you got any "never feed" advice from if you can (a vet, a hatchery, a book). Opinions are welcome; sources are better.
Feed & Nutrition