I second doing the ducks first & seeing how clean you can keep the water (clean as in ammonia/nitrites not dirt). You will need a MAJOR filter system, preferably a lot of duck resistant aquatic plants, & at least weekly water changes to keep fish alive in that size pond. Your best bet will be regular comet goldfish (aka feeder fish). Plecos (aka sucker fish) are actually pretty sensitive to ammonia, which is normal for scaleless fish species. They are also a tropical fish so won't generally overwinter (yes, I know, there is an exception for everything). Plecos, contrary to popular belief, don't eat waste. They eat vegetable matter including most types of algae, dead fish, & the fish food your other fish get. Live plants will really help with ammonia, the faster growing (like water hyacinth) the better but ducks are hard on plants.
You'll have to share pictures of what you end up with!
