because it's only a 20 gallon, i don't think i need a skimmer( just frequent water changes-- as for flow, i will be using one rio 1700 powerhead-- and as for fitration, i will be using live sand and live rock with mangrove trees to remove nitrates-- i will be keeping mainly softies, but will incorporate some hard corals at the very top cause with 135 watts @6.5 watts per gallon, everything should grow nicely or at least i hope