I was wondering about this very topic when i first started up my nano. I have an aquac remora pro skimmer on my 55 gal and i love it, wouldnt run a reef that suze without one, but it really seems like more of a pain to put one on the 12 gal cube, since i'd have to cut into the hood and get a skimmer small enough to fit. Most of the people I've talked to don't have one and their tanks run fine. I just keep up with water changes so quality doesn't become a problem.