Sphagnum moss is safe, absolutely. If you're buying it in one of the bulk bags from a hardware or garden supply store, make sure that it doesn't have any additives of any kind. Some people still buy it in bulk like that and then bake it on low heat in the oven for an hour or so to kill off anything that might be living in it, such as grubs or insects of some sort. Or the stuff you buy at the pet store is another option. More expensive for a smaller amount of but if that's all you need, well... Hope that helps.