I have a 45g fuge and a separate 45g DSB and I run a bit higher flow. The fuge and DSB are about 10x (the DSB is half the water volume because of the 8" deep sand volume, so I cut the amount of water in half with a bypass, but the turnover is still about 10 times). And if you look at reefs or the ocean in general, macro algae does just as well (maybe better) in higher flow areas than it does in low flow areas. And it's going to pull nitrates and phosphates out of the water no matter how fast (within reason) it's flowing by.