I got my gray tree frog much sooner than I expected so I've started converting my 10 gallon terrarium (I was hoping to be able to do this in the revers order, sigh). I'll have a few questions very shortly and I have a quick one now. The care sheet recommends top soil as the substrate, but how do you make sure there are no additives in it? When I set up my snake terrarium I bought a bag of organic top soil at a dedicated gardening center, but even they couldn't assure me that it did not contain organic additives (like manure), which I figure wouldn't be too bad for a snake, but I have doubts about how amphibians would react.