Interested to see a contest about it. I have this going for many months now.
My top tip is to make the rockscape as one single piece. It's pretty easy with NSA building technique, superglue with accelerator.
And no sand. That way, water change will be simply take the scape out, or not, and pour the whole tank out then fill it back in.
The best way to start the tank is, after the single piece rockscape is built, mount all kinds of corals in it, then put it in your display to let them settle in and grow in, then put it into the mini tank.
If I'm serious in winning the contest, I can just leave it in my main tank. Took it out to the mini tank to take a picture once a month.