I’m setting a 39 gallon semi-reef, live sand and rocks, a couple of powerheads for circulation a protein skimmer and a double fluorescent white + blue or a single PC as for coral maybe a few hardy species in the future, but for now it will be just live rock and anything it will bring attached to it, a few invertebrates for cleaning and fish, question is do I need any other type of filtration besides the skimmer? Any help will be greatly appreciated. Thanks