i have a 180 corner Tanganyika setup, with pearl reef sand, and a compact 50/50 light. The black painted background makes my Frontosa look amazing!!! Use water based black primer if you can find it, or any flat black water based paint. It works awesome!!!!!
If you plan on photographing your fish go with black. It really makes the colors on the fish pop and it's easier to clean up the bubbles and dust that show up.