Having a background can reduce stress and hide clutter. Paint... window tint and even a thin sheet of colored plastic are all options. The fish show up a lot better and you have a much neater set up. That said theres really nothing wroung with a simple bare bottom no frills tank. My wife and I have several closely spaced fish tanks and we discovered that the fish react to each other through the glass. We are planning on putting dividers between the tanks very soon to rerduce the risk of stress.