cultured stone ?

[Mrfish55]

I wouldn't put it in my tank, I just installed the stuff on my house and had to make a few cuts, it's full of all kinds of fillers and fibers to lessen manufacturing costs and make it lightweight, my best guess is it is full of recycled "stuff" and without knowing exactly what those fillers are it runs the risk of leaching who knows what into your water, sounds like a good idea but personally I would not try it.