Friends and I in some disagreement about how often we need to move our chicken tractor. We have 13 chickens in it and it's 4 feet by 7 feet. I think once a week would be good, but they're little still and in tall grass and they don't peck it all the way down in a week. I just think it's a good sanitary measure to move it once a week because the grass gets matted and poopy. Others think they need to get further down to dirt to get enough grit. Anyone have opinions? Thanks!