fishdudein
Fishaholic
A lot of my smaller breeding tanks are bare bottomed, the fish don't seem to mind one way or the other. When I first tried this concept, the glare off the bottom did seem to affect them, I got around this by painting the bottom of the tanks (outside underneath part of course). Might want to consider this option with your discus tank, I know they can be very susceptible to stress-related disease. I found that a nice coffee brown color works very well and looks more natural also. In my cory breeding tanks, I will add a small handful of gravel, just enough to give them something to root around in, it makes a difference.