I've done that. The two decoys are going to creep together and start bouncing off of each other. If you put something in the middle and tie the cord to it like a dowell rod that floats they stay apart and work pretty good. I used a 12volt gel cell in a goose floater. You might also try turning your pump discharge tube down. It will give just as much motion without spraying water everywhere, plus it stirs up mud and crap down low and makes the water muddy like feeding ducks in shallows do.
Nothing to see here, move along now!