I have been asked again what should I use for ground cover in a fixed chicken run, to be honest I hate fixed chicken runs as diseases and worms can build up here, movable runs are so much better but of course we are not all so lucky. So in this situation I would suggest small chipped bark to about 1″ deep, deeper if you can. If the peices are too large the chickens can not dig it about and it will become caked with droppings very quickly and will need to be changed very often. Ideally on a 10′ x 6′ run with 6 chickens I would suggest changing every 3-4 weeks if the run is covered but if it is rained on then this will give a life of 4-12 weeks. If it smells dont delay change it. Please dont forget in a fixed run you must worm your birds on a very regular basis.