Oak leaf litter is ideal for bioactive terrariums due to its durability and high tannin content, which resist decay and mold growth. It provides essential cover and food for microfauna like isopods and springtails, promoting a balanced ecosystem. The natural decomposition process of oak leaves also enriches the substrate, supporting plant health. Oak leaf litter is a simple, effective way to enhance the functionality and aesthetics of a bioactive terrarium.