When I was re-doing my tank during a move this past summer, I decided to get really wild. I got some of that 'fleckstone' spraypaint. It goes on and looks like a sandstone finish. I got the black & white stuff and that turned out pretty good, but I bet a true sandstone color (maybe with a dark grey cover-coat) would look awesome. Maybe I'll have to set up my 125 again to try that out!
Mine is black..and I like it but would honestly rather have it clear. Im getting so much corralin growth that it will eventually cover the whole back anyways...but for the time being, i would have liked to be able to see the back of my tank..i feel im missing out on a whole OTHER SIDE of my system
I like blue if you have room in the back to keep it clean so you can see the blue. Otherwise it probably does not matter. Let it get coated with coraline algae.
Clear. Mounted a cheapie mirror on the wall 6" behind the tank so I can see behind the rockwork, never knew what I was missing, plus it makes the tank look so much deeper.
I too like the black. I ordered my 80 with a black back. My 10 gallon was set up clear then replaced with a 30 that I painted black. I like the black much better. Shows the colors better. Mirror might be kinda cool but I haven't tried it. The post about getting to see the back sparked a little interest. Not enough to change my current setup but something to think about haha.
The 'back' of the tank usually looks best when black for contrast and to soften the color of any algae (good or bad) that may grow there and rarely is ever cleaned off. At least in my tank.