Umm..why do my bearded dragons keep burying their dishes?

Our bearded dragons keep digging in their calcium sand. they dig in it so much that the sand ends up in their dishes, in their lettuce, fruit/meal worms/crickets/grasshopper, and water dish. they fill up their dishes so much with the sand they dont have enough to drink cause they fill up their water dish and they usually end up burying their food too. oh and they keep trying to climb the side of the tank. this is our first time owning bearded dragons, so im just curious if theres something wrong here? and if theres a way to break them of this habit.