You don't need additional filters...
Live Rock and Live Sand act as a natural filter. In addition, Refugiums will help lower nitrates and phosphates. A protein skimmer removes organic wastes, etc. The combination of those is all the filter you should need.
If you don't have live rock, live sand, etc., then you may need more mechanical filtration like wet/dry's, etc.
What other suggestions are you looking for? Hang on filters like bio-wheels?