Crushed limestone works, but any gravel has big and little pieces. A medium driveway gravel (called AA last time I bought it) is great too.I thought about putting a piece of plywood over it. It's an old sandbox fort (my coop and run is a renovated wooden playset) so it would be easy to lay a wooden floor over the edges. My concern with that is creating a haven for the friendly (NOT) neighborhood groundhog - or worse, rats! We're going to try gravel, next, I think. Sand wasn't enough and mulch brought in a nasty mold that cost me three of my beautiful boys - never again!
What kind of gravel? Nothing sharp, for fear of bumblefoot. I can get pea gravel fairly inexpensively, but how small? And what about crusher-run, like we use for driveways? Would that have anything toxic in it? I also had an idea of using natural wood discs - crosscuts from firewood. We have a fairly large downed tree that would make rounds about 8-12 inches. I thought about putting down a layer of those & filling in with sand or oyster shell - like pavers. It's a lot of work ... but until everything opens up again and the second wave runs through, I really don't have anywhere pressing to be ....