why not just take a piece of paper...buy lots of differnt shades of black, brown, tan and white spray paint and just mist it from a distance...no scratches...much cheaper...easy to get the look you want
Thats what I would do
Actually thats a lie...I would just paint it black
The sandpaper I use is only coarse on 1 side. The other is like plain paper. Seems like a good idea if you used black sandpaper. It wouldnt hurt fish that much.