In the past, I've used shaped styrofoam for hobby applications and I was wondering if it is safe to use in a terrarium. I speaking specifically of the thick panels (appr. 2") available at home depot. I was thinking of using them as a base to build a water course in the terrarium I'm working on. I'd use the black silicone/ coco mix to cover the sides and use gravel siliconed in place along the waterway bed. Also thinking of using it on the back of the tank. Any thoughts? Thanks again.