Tropical Foam Inserts designed for the Zoo Med Naturalistic Terrariums or Exo Terra terrariums! Each piece is hand made and hand painted with animal safe material! They have a pre-cut area for a pump to create a natural looking waterfall and pond area! Each piece is uniquely designed and cut, including the caverns and craters! If you use a submersible pump (like the exo terra one we sell), the foam will act as a biological filter for the water! Over time, healthy bacteria will build up creating a self-sustaining environment!