I've got some anthellia and some GSP in my tank.  I had the GPS(all 3 polyps of it) glued to the back of the tank, yet knocked it off by accident, and thought I'd lost it(couldn't find it after moving stuff around).  So I was planning on glueing the anthellia(on a bit of rock) to the back instead.  I'd like a "natural" background for the tank, instead of being able to see my window, or having to mess with a background.  I know both would gladly grow on the back, but which should I put on there?  The other is likely to go on the bottom of the tank.