Actually, some would argue against that. Most of what you put in a fuge (macro algae) uses the excess nutrients in the water that a skimmer helps take out. So if the skimmer filters the water first you kind of starve the fuge. Some of the sumps I have seen and the two that I built for myself over the years actually split the drain line, one part going to the main sump area and feeding the skimmer and then a smaller part from the drain line feeding straight to the fuge. Then both areas drain into a commmon section that feeds the return pump.