I used to run my 12g AquaPod without a skimmer. Just used the sponge that came with the tank, and a chamber modded into a chaeto refugium. I fed mysis, cyclopeeze, oyster eggs, and phyto at least once a week. My growth was good, even under the stock PC lighting the tank came with. I did then and do now a 10% waterchange once or twice a week. Only one problem though, Bryopsis! After I upgraded to a 70w MH, it got even worse and after a couple weeks of pulling Bryopsis out twice a week to keep it from overgrowing the coral I changed things up. I bought a HOB skimmer rated for 70 gallons and removed the sponge and refugium. It is now my only form of filtration and I would never go back. I now only feed once a month, and not nearly as much as I used to and still get as good if not better growth. I am also always sure to do a waterchange the day after feeding, and the Bryopsis finally struggles to grow. The Caulerpa still requires weekly harvesting, but doesn't grow at anywhere near the rate it used to.
I would have to say my growth is better now that I keep much cleaner water, but the lighting is probably more responsible for that. I would consider a skimmer a solution to a problem, and if you don't have that problem I wouldn't worry about it.