So I have a relatively new saltwater tank. I have live rock and an external power filter for filtration. From what I've read online and in books a protein skimmer is an essential part to every successful saltwater aquarium. I'm looking for some advice on what would be the best setup for my aquarium. Its a 55 gallon FOWLR for now and I have two damselfish and a firefish in it. I don't foresee getting into any real corals with it but maybe an anemone someday. Anyway I'm starting to see a bunch of crud and what looks like an oily substance floating on top of the water from tine to time so I figured this means its time to make the investment. Any pointers would be much appreciated!