rowly, i had 6 ducks in my lake for about 6 months. other than stealing my fish feed, they caused me absolutely no problems (although the white pekings did leave a bit of a mess with their white feathers). i could not find any damage to my shoreline nor my plants along the shore. they were fun to have and to watch. we even hoped they would hatch some young. i'd make sure though that you never plan to feed your fish. domestic ducks and fish feed just won't work. enjoy them!
jim, i shouldn't have to explain nor justify myself; but i will. our ducks were pets. we enjoyed them. when we decided that they had to go, we had dificulty catching them without hurting them in the process. no one in my home "enjoyed" killing them. i apologise if my post read that way. i took the opportunity as a father to teach my teenage son how to use a shotgun. that was the "fun" part. just like catching the lmb with my son is "fun". a 12 guage was the most humane way we could think of to get them into our freezer. we do after all, live on a ranch. we raise a lot of the food we put onto our table, including chickens and turkeys and ducks; so my freezer was where they ended up. that's the last i'll say about it. jb