Lol for decor, if you cant find anything big enough, then why not try adding a bunch of plants that grow fairly large, adding a few decent size pieces of limestone or something like that, get some big pieces of drift wood.. Sure for a tank that size it will probably be fairly expensive to deck it out in all that kind of stuff but hey.. it will look wicked when its finished!!! Also, why not add a little diver ornament... that would just be epic....