Protein skimmers are good devices, I had one on my 55 gallon reef tank, but sold off the tank. The reason why it was there in the first place was more to extend the time period between water changes since I lived a fair distance from the LFS and didnt like lugging home bottles of water, and the larger the tank, the more water you are changing on a weekly basis.
But now I have 3 12 gallon nanos and dont see the need for a protein skimmer since the amount of water that I change on a weekly basis is minimal, like 1 to 2 gallons per tank per week which keeps the nitrates down and is not expensive, like maybe $4 to $5 /week (because I buy the premixed water, and I now keep 4, five gallon containers so that I dont have to go to the LFS very often, and thus avoid temptation to buy that new addition to the tank.)