So I have 6 chickens in a 8 x 7 ft run/coop. The first month I put down bark in their run but this got boggy and damp with the rain and the chicken poop. This month I tried sand hoping it would have better drainage but that got damp all the way through and was therefore impossible to sieve out the poo. It then got clogged within a few days of poop and feathers and so I removed it all at the end of the month. Now they are just on the concrete while I decide what is best to put down? What do you guys use in your runs and how do you stop the poop building up and or keep relatively clean. I'm not considering only having 3 chickens because of the mess every few days. I literally want to remove all the substrate every few days and start again.