Coconut fiber works fantastic, you should be able to pick it up at a local petstore. They usually keep themselves burrowed most of the time, so make sure there's a few inches for them to hide in. I know I rarely ever see my guy. When I put crickets, you'll see eyes pop out of the substrate out of no where, and occasionally sits in the water bowl. Thats about it haha. They don't really have a use for plants, so its pretty well free range on what you like. I like big leafy things personally. You can even pick up some good fake ones from any place that sells aquariums/fish.