You are talking about two different functions. The refug is to house more livesand, microalgae, rubble rock, ect. to balance the system. By having the microalgae, in basic terms, sucks the nutrients from the tank (in order to grow), rather than growing hair algae and other nuscense algaes in the tank. The protein skimmer is the wave, which is natures way of disposing of waste found in the ocean. When a wave comes ashore the white foam on the beach is the excess waste. the skimmer does this by pulling the waste out of the tank and into the holding cup which you then dump out. As for the nano tank? I have the 12g aquapod and my LFS said I shouldn't need a skimmer and that the nano skimmer that is sold for this model is junk. These tanks are built with surface skimmers to allow that junk film that collects on the surface to go into the filter system ( just direct the powerhead to aggitate the surface) and with frequent water changes we are basicilly keeping the water fresh.
IMO if you have the room for a refug, by all means do it to create more of a balanced system. As for the skimmer (depends on your nano size) see how your corals react!
Hope this helped, I like to keep it simple- certainly not a scientist!
