I live in Illinois and have had my girls for a year now. Their runs are covered and the floor is dirt. The dirt has became very hard. I was thinking of tilling them to break up the dirt then add mulch but I am on the fence post with a decision. I am looking into the best run coverage material. With sand they cannot scratch around for bugs, keeps their feet clean, and they can dust bathe in it. On the other hand with mulch...they can scratch around for bugs. The mulch will dry out since the runs are covered. What is your choice of material for runs?