That "hole" has long since been plugged with gravel. They have created a few more spots one or more like to hide and I've left them if they are safe (relatively smooth areas), plus added a couple of fake plants for hiding. My brown ones mostly hide; my green ones are mostly out. The chubby one, for a while, liked to hang out under a fake slate piece on the waterfall area with water running over it. Now he likes to mostly hang out among the fake plants.