[melev]

For me, flow needs to be tailored to match the coral's requirements rather than meeting some magical number. There are a few standards, like the minimum of 10x turnover for a basic system, but there are some corals designed for tons of flow while others prefer a gentler amount.

In a reef tank, flow usually needs to be greater along the top, which is easy since very little is in the way to cause an obstruction. Medium flow occurs around the rockwork, and low flow usually happens over the sand bed because we don't want the sand blowing everywhere.