how old are your ducks? are they in a confined small area?? My ducks are free range, and they sleep on either straw or hay in the barn that is on the floor, or they sleep in the grass. I don't have the mess cause they don't go in the chicken house.
I did have them in the chicken house and the big mess was mostly because they mess up the water! they will empty any waterer pretty fast. I have heard of using bottles, the upside down ones you use for rabbits and they are better.
the water is what makes the bedding worse!