We have 13 ducks on our farm pond. Pond is approx. 100' x 80' and was stocked with fish about 20 years ago. Very established pond with lots of "stuff" living in it. Ducks also free range over as much of the acreage as they wish, but never get too far away from the pond. How much food do you think they are getting on their own? How much (and what) do they need to be fed in addition to what they are eating on the pond?