J.B.;814170 wrote: Mike, sounds like you have your mind made-up for spray, so this isn't for you, but for anyone else who is reading along, who might be on the fence.
The poster-board idea is good for a while, but the first time you or a fish splashes water over the back, it's done (ask me how I know this)</em>. The only "paper-type" backgrounds that will endure are the coated ones you can buy in your LFSs. A lot of folks will tape these on, but there's another, cleaner way to do it. Try not to giggle...take some K-Y Jelly and squeeze a generous amount all over the back of your tank. Now apply the coated background and squeegee it smooth. Allow it to dry for a bit and it will stick there on it's own, without tape hanging around the edge of your tank. It forms somewhat of a seal and will not allow water to get between the glass and the background.
On thing to keep in mind, you can't just slide the tank out, like a couch or something to redo it, so you really need think through this.