With a tank that small, I was always under the assumption that the more compact everything is the better, by adding a skimmer you those that feature. Ever since I made the change that I talked about above, I've seen tremendous improvement in
coral growth and water clarity. I'd much rather buy and air pump and stone vs. buying a skimmer that 1) may not work as well as larger skimmers do for larger tanks and 2) destroy the look of a "compact" nano.
I also have a 29g, which I use a 65f CSS on. I'm not saying skimming is a bad idea, I'm just saying there are other, perhaps more inventive/cheaper ways to get things done.
Just my experience
LS