My fish room is almost done! The fish room shares a wall with the living room of the house and my plan is to install a flush mount tank in the wall. I'd like to build it with a glass front and a poured back, bottom and sides so I can hide plumbing in the walls and floor. I see tanks at zoo's and aquariums with a "rock" type back wall. Does anyone know of a reef safe material to make the wall out of?