I know the live rock will aid in the filtration along with a skimmer but I would imagine I would probably need more I just dont know what too use.
Growing up with only freshwater aquaria, I also had trouble believing that somehow rock and sand could be the entire base of filtration. But, it really is true that LR
can and will outcompete any kind of manmade filtration and with 75-100lbs in a 55g, I don't think you will have an issue. Bob Fenner and Anthony Calfo's new Reef Invertebrates
book gives great information in the beginning on the principles of such natural filtration.