Medicated Starter/Grower is safe for ducks and other waterfowl, provided that the medication in the feed is Amprolium. Bacitracin is also safe but not as common. Medicated feed was once considered toxic to waterfowl due to the arsenic and sulfa based products that were typically used. Since Amprolium is now widely used as a coccidiostat in most medicated feeds, this is no longer a concern, and is probably beneficial. (Amprolium is so safe that it is approved for the use in laying hens.) I use medicated Starter/Grower exclusively for my waterfowl.