I used to have black sand and a black background. Depending on the fish you want to keep, it can be too dark. I had a Chinese Perch that just disappeared from the front view. It would always stay in the back, but I couldn't see him unless I looked at the side to see exactly where he was. However, I had a Silver Arowana in there that looked great. Dats and Pbass were okay in there, GT looked good, etc. Anything light or with a lot of color will surely look good in a blacked out tank.