I had to let all of you know about the greatest addition to my bunnies' condo. I bought another large tub like the one where they spend so much time eating hay and filled it about 1/4 full of sandbox sand. They love it! They dig, scratch, and lay in it for hours. My male has learned to balance himself on the edge on his back feet and throw sand over the side, then hop out - inspect the depth of his damage and hop back on for more. It's great excercise and they seem to really like that bit of outdoors-indoors feel.