I used Greatstuff, It looks really nice and I have pics of the whole process but decided not to post them because I failed. This thing is so buoyant that a couple of bricks will not even hold it underwater! hehe, Guess my next try will be with cement and foam.
So be advised. If you want a 100% greatstuff background you'll need a cinder block to hold it down. I guess there is some pond foam that is neutrally buoyant that would work better.
So be advised. If you want a 100% greatstuff background you'll need a cinder block to hold it down. I guess there is some pond foam that is neutrally buoyant that would work better.