I used them routinely for a while, years ago when I had horses along with my chickens. Despite good manure management I never saw satisfactory results with the fly predators. We're on rural acreage and also have neighbors essentially operating a CAFO, so I'm certain flies from other sources contributed to my fly problem.
Since my heart horse went to the Rainbow Bridge two years ago, my fly population has almost gone away. I currently have a small flock of five hens.
Depending upon your setup they might work well, so I'd give it a try. Follow instructions accurately and remember--chickens and other birds will likely eat the fly predator larvae if they find them. Also remember--pesticide use around your fly predators will kill them.
