Magnolia leaves are one of the longer lasting leaves that you can use in a terrarium or vivarium. They are very leathery feeling and make a great addition to a naturalistic decor.
Leaf litter not only helps with providing a naturalistic appearance, but the leaves also provide hiding spots for animals such as dart frogs. Additionally, microfauna like sprintails and isopods will use the decomposing leaves as food. In the forest, the leaf litter may be several inches thick. Typically in tanks, you want to have the leaves at least a few layers deep and you should routinely add leaves as you see them decomposing