I tried black with play sand and it was too dark for my liking so I switched it to blue back with white sand. I like it a lot better. Looks brighter.
All you have to do is paint the outside of the back of the tank with paint i just got some acrylic paint and rolled it on the backno back grounds here except looking out the Windows. some day i do need to get one on the 180, just hard to find a back ground large enof.