I have one of those fossil ones it has tons of holes, but I found it to be a problem, because the crickets will hide in that rock badly all day long and won't come out until the babies have gone to sleep...when I finally took the rock out for cleaning and I hit it tons of crickets came out. Had to be 2-3 dz. So that is why I was wondering about the slate. We leave near rivers, but there is just to much snow and ice to go out there and look.