Well I have a 12g Nanocube with no fish. I have zoas, LPS xenia and SPS. I don't keep an eye on it, I don't do water changes, don't add any suppliments, and just don't do anything but huge water top offs every couple days lol. I pretty much do everything you are not supposed to. My one piece of SPS under 48W of PC lighting has grown quite a bit since I got it 6 months ago (I got it when it was a 1/2" single branch now its a few branches, about 2 1/2" tall and 3" wide) my xenia grows out of control which i bring to my LFS for store credit. My zoas grow at a steady rate and my hammer has gone from 5 heads to 8 heads. I did have a hair algae problem that is clearing up (hair algae grew because tank was next to the window). I don't use any filter media like charcoal, filter floss or filter pads. I use my nano skimmer just to produce air bubbles because I realized when that it wasn't running all my coral looked like crap.
I used to have two clowns, and was keeping the tank the same way but people were telling me I was going to have trouble if i didn't do water changes and keep up with the maintenance. So I did a water change, both the clowns got stressed and got ich (I woke up the next morning and realized it). I setup a QT and tried to get them better but unfortunetly they couldn't shake it. So since that day I decided I was going to stick with what is working, and that was just letting the tank take care of itself.
I'm not saying this will work for everyone, or anyone.. but it has worked for me.
-Brian