I have nothing serparating the gravel from the coco fiber, but it is large gravel and I dont think it poses an impaction risk. He feeds off tongs (to avoid eating anything he isnt supposed to). I have water conditioner I use for my sons fish, so I willl start treating his water dish water. He is definitely a burrower. At one point I had closer to 4" of coco fiber in his enclosure, but he would dig down to the gravel layer for 4-5 days at a time. Idk if that info is of any use. Are there any disadvantages to using a intrared bulb full time?