i just buy nutrena all flock. It is good for any poultry. So both your chickens and ducks can eat it. Purina also sells flock raiser that is the same thing but its crumbles instead of pellets.
We stopped using Nutrena feeds after November when the local distributor told our feed store they had to buy the entire truck load or get nothing. Since our feed store likes to turn over stock in a timely manor and not have bags laying around for months this wasn't doable.
feed mix for waterfowl:
Mazuri waterfowl feed (great small flattened round shape, little no waste)
BOSS
Oats
Flock raiser
Handful of scratch or two tossed out for them in the AM as they turned out for the day.
Ducks are all feed in the AM when turned out. Geese are feed in the PM in their stalls. Chickens have feed available 24/7
Greens are chopped up (kale, collard, dandelion ect) and given mid day
Fruits and peas given once a week with greens.
We also seed winter rye this time of the year and they love nibbling it up when it sprouts.
Our call ducks are in raised breeder pens and have rabbit hopper style feeders in the pens. We use stainless bowls for greens as they are easily cleaned up.
My ducks and geese get dog food, oddly. I buy a brand with small kibbles they can swallow and they don't lose them. With 34 birds and 5 dogs I go through a 50 lb bag every 5 days for 22$, but my waterfowl's feathers are fantastic, my eggs are glorious and even the flesh on my culls is tasty and lean.