Ducks will make the water fertile = good for watering garden, bad for keeping vegitation/algae under control in the pond.
How would ducks provide fish food? Perhaps a roundabout way for the tilapia via FA.
Get some kind of aeration system. Don't rely on the ducks. Kind of a sign already with the tadpoles dying that the ducks won't provide a good enough source.
We'll see what other think about stocking plans, but would you be open to the idea of a few CC. They would use a differnt part of the water system besides tilapia, so you could have both. You are only going to get so many #'s of fish out of a small pond.
Are you open to the idea of feeding fish?