The term "bioactive" is used to describe a miniature ecosystem created in a terrarium or vivarium. In a functional bioactive habitat, small invertebrates (aka clean-up crew) eliminate waste from your pet to make nutrients available for live plants to consume. This incredible living network forms a balance that can reduce maintenance of your habitat while enhancing natural appearance. The right substrate mix is critical to a successful bioactive habitat. The contents of this kit were carefully selected. to help your pets, plants, and clean-up crew collectively flourish.