I was kicking this idea around about 6 months ago just before i moved... creating a 3D background by spraying on a layer of this expanding insulation foam,, the idea was that coral frags, rocks and other things could be stuck into it and would grow onto it, making it look like part of the natural rockscape.. i decided against it because i thought the stuff might be toxic to fish and corals but now i'm re-thinking this idea. once it cures and hardens (which takes about 1-2 hrs) its just like styrofoam. Then i just read an article in Reefkeeping that someone has already done it and it is in their tank... This is a very cool idea to me as it can create a natural looking backgound and hide overflows and such, anyone have any comments, ideas or information on this subject,,???