I use sheet moss over coco fibre so the coco fibre doesn't dry out and stick to the frogs. The sheet moss is the same thing they use around bonzai trees. It is green and looks like miniture grass. It also adds color to the tank. It can not be soaking in water because it will turn brown. It holds up well to normal moisture from misting, water fall moisture and frog sweat. It is inexpensive and can be found at Michaels or most craft stores. I would also agree and get rid of the under tank heater as that could dry out your substrate. If you have a cool house you could move the heat mat to the side of the tank if you feel you need it.