Hey now... stop making fun of my artistry!
I was thinking of incorporating some coral silhouettes like elkhorn, etc. but I think the more detail you provide the more you run the risk of it looking cheesy if it's not quite right, kwim?
I am getting a couple of different kinds of grit to try out on the acrylic. My preferred result still would be for the rocks to be just visible as very fuzzy images.
Something that's there to provide that feeling of depth but ideally unless one pays attention to it doesn't draw then viewers eye to it.
corals in the actual tank shall be the focus,fake rocks in the box should be just a faint image in the back.