Hi this was a while back so since then I have sorted it out. I used a mixture of organic top soil, orchid bark, and leaf litter collected from the woods, I have added tropical springtails, tropical woodlice, earthworms and have a colony of domino cockroaches in there too! Al the little critters break down the waste and dead leaves so I never have to clean it out! and then the critters waste is absorbed by the plants! Its like a little eco system, Its called a bioactive substrate and well worth doing!
I havent covered it with moss only leaf litter so its perfectly safe!