We raised ducks for years when I was growing up. If you ain't flushing it every week well you're gonna end up with a tub full of duck crap. If you have the area to do it you should dig a pond of about 1/2 acre in size and at least 8 feet deep, that will take care of your problem and it's a great place to put catfish, bass, crappie and bream in and have a steady supply of fresh fish when you need them.