As someone who started off with sand in our run, I feel I can say - don't do it!! The first year I loved it. The second year, not so much, but didn't want to move it. This year had me, with a shovel and wheelbarrow, moving a pickup truck load of sand out of the run because it started to smell so bad even after scooping at least twice a day - every day.I thought course sand was the most sanitary. The bedding/litter system seems kind of gross because it is layers upon layers of poop. Doesn't that harbor bacteria? Doesn't it smell bad?
Granted a coop will stay dryer than a covered run, but just the poop alone will add plenty of moisture especially if you don't want to scoop it every day.
We use pine shavings in the coops and a mix of hardwood mulch, straw, used shavings and pine needles in the run
