I've been looking for a simple, cheap background for my tank. I haven't had good success with the typical aquarium backgrounds. Last week I was at the dollar store and picked up some colored cellophane to try and it worked well. It clings to the back of the tank like glue, no tape needed, and it gives a bit of a subtle backdrop to the tank. I was even thinking that I can buy special types for the holidays, like candycanes for Xmas or something
Here's a pic. There are a lot of wrinkles here cause I'd just put it on, but I got those all smothed out yesterday.