I have chickens and ducks in the same coop -its 2 story and the chickens tend to stay on the top level. The bottom level is the ground/grass and we move the coop every few weeks to let the ground heal. Everyone is free range during the day but the ducks must spend the entire night destroying the ground in the coop. Anyways a few months back someone mentioned putting river gravel on the ground. And then I read about a layer of rocks covered with landscape fabric covered with sand. So my husband put a thin layer of sand on the ground which the ducks loved and made a HUGE stinky mess out of. I just came from our local place that sells that stuff and they had never heard of "river sand" their coursest sand was cement sand and seemed to me like regular sand with a few pebbles (ie same problem as above) BUT they had something called pea gravel- which looked like round aquarium rocks (in my laymens opinion). It was only $41/yd and they guessed I needed half a yard. The rocks looked smooth and round so they wouldn't hurt anyones feet but will it work?? Or does someone have a better suggestion?? I'm trying to make a place the coop can stay for months at a time (its REALLY heavy with no wheels) that will be more hygenic and less smelly. And flies are an issue. We live on the central coast of cali- so weather isn't a big issue (in our most extreme winters it gets down to low 30s) other than the occasional rain storm.