There are alot of skimmers that are recirculating, meaning that the skimmer pump's sole purpose is to make foam. Thus requiring a supply to feed the skimmer. You are probably going to have to spend a little more scratch if you want a "good" skimmer that your going to be happy with, then again you might find a good deal on a used one.
This would be a good choice for your tank and a good deal IMO.