I am ordering 4 yards of sand for our new duck yard and my options are Buckshot, Wash FA1, or Filter sand. Any advice? Want it to be safe and gentle for duck feet! Also, our plan is to run perforated drainage tile around the edges of the 15x20 enclosure. My husband is digging down and sloping the area toward tiles and out the back which is near edge of ravine. We are going to put 6 inches of sand on top. The top couple inches will probably be above ground level. How does this sound? We have definitely never done anything like this before! Should we put down any pea gravel first or just the sand? Our soil has clay, but isn't pure clay.