if you'd like to prepare a real cool background, then do this: Get paper/cardboard the size of the back of your tank. Spray construction foam (polyurethane) on it, let cure. This way, you create a 3D background. Paint with oil-based paint and let the colors flow into each other. Use brown and green, but also bright yellow (sparingly). It'll look awesome. I do that for all of my tanks. It looks real natural.
I'm working on it. The problem is that I do not have a digital camera. Things take a while when you have to fill up a 24 roll of film. But I promise to start a post just with pics once I get them developed and scanned.