There is 3.75' gap between the wall and tank (enough space for Mp40's) which gives me some access. Not sure what I want to use for the back wall yet. Might try one of those cheap aquarium black backgrounds to start and go from there.If the tank is already in place, how do you put on a black background?? I have a peninsula nano in a similar situation where the one side is against a wall. That side is covered by coralline. Definitely something I wish I thought of earlier.