The children's area of our museum has this toy. They keep healthy worms in it at all times (I asked). However, we have yet to see a single worm and we check every time we go (we've been doing this for over 2 years). The worms never bore near the sides.The toy is also cheaply made, the area in the picture you see that looks like rock is styrofoam. It isn't very big. And the sides scratch easily. The dark covers on either side are cheap cardboard and don't last long either. Our museum attendants have had to replace them with thick black cardboard pieces. Even with the thicker, darker covers against the plastic sides, the worms won't dig near the sides.This toy is a good concept, but poorly done and a total waste of money.