I honestly don't think nano's require them. I myself do a weekly water change of 7 gallons. Running a skimmer for a week might take out a quart or half gallon of skimmate. My logic is that the 7 gallons I take out probably has at least a half gallon worth of skimmate in it, therefore a skimmer would only aid. But, with my 7 gal water change on a 29 gal tank, I always have perfect readings, so I think I've proven that nano's do not require a skimmer, just consistent water changes. Also, it takes no time to change 7 gal of water, maybe 60 seconds to take 7 gallons out, and 60 seconds to pout 7 gallons in. Besides, you have to do water changes anyway......
I prefer to use my middle chamber as a refugium with chaeto and LR rubble. Also, a 9w Coralife UV sterilizer fits perfectly on top of the 2nd and third chambers without modifying the lid. The UV costs 75 + 15 for a powerhead to drive it. I turn it off when I feed DTs live phyto and turn on the next day.