Bio active substrates are designed to allow the maintenance of living ecosystems inside the terrarium. ProRep Bio-Life substrate 10l is carefully blended from a mixture of ingredients to provide the optimum combination of structure, PH and nutrient content for plants from arid environments. When used in a planted terrarium, a living ecosystem can be created where the terrarium occupants co-exist with the plants and microorganisms to create a self-sustaining ecosystem. The microorganisms digest waste material, which is in turn taken up by the plants for growth, locking away harmful nitrogen while creating a living, natural habitat. Because an arid environment set up is dry, with low humidity, then it can be more difficult to maintain than forest set ups. With the proper design however, it is possible to recreate a moist zone in the base of the terrarium to mimic the moisture commonly found underground in deserts. This moist zone provides a reservoir of water which plants and microorganisms can access, while the surface of the substrate remains dry.