Zoo Med Excavator Clay Burrowing Substrate for Reptiles. Bring your reptile’s natural habitat to his terrarium with Zoo Med’s Excavator Clay Burrowing Substrate. Mimic your sidekick’s natural habitat by using water to mold the clay into tunnels and mounds—the clay is designed to hold the tunnel shape to help prevent it from collapsing as your pet wanders through. Made with zero dyes or chemicals Satisfy their natural burrowing and digging instincts Holds the shape of tunnels to help prevent them from collapsing Available Size: 10 lb