my runners have full access to pellets, grit, and oyster shell at all times. I don' refill their bowl until they finish. If you got yourself show quality runners you plan on exhibiting, i recommend going by the diet in Storeys Guide to raising ducks for sure... If not, you can feed twice a day, or feed all the time... ducks in general wont gorge on normal pellets.
My girls eat Mazuri waterfowl feed in the morning. (keeping their dish full all day up til bed time)
At night they get a big dish of treats (no bread or grains) I usually put lettuce, peas, tomatoes, banana, any other ducky safe veggies, and often their own eggs. I sprinkle grit over top of that and they also get 2 table spoons of Mana Pro Conditioning suplement.
I need to start on some oystershell... But that about cover's it!
Emily