For a totally different perspective.
I use a closed loop that attempts to deliver laminar flow to the entire length of my rock walls. I created the system for seahorses as they don't do well in the focused blast of powerheads. Bear in mind that it is a softie oriented reef and I don't keep SPS. The idea is an adaptation of the UGJ's used in big cichlid tanks.
I run 2 M.J. 1000's in line connected to about 16' of 1/2" PVC. This is laid out beneath the substrate along the front and back of my rock walls and drilled every inch with 1/8th holes. When I tested the system I had surface agitation across the entire surface of my tank (straight up from the bottom) and it has worked well so far. The "mini jets" are constantly kicking detritus up into the water column to be siphoned off by the horizontal overflow.
I don't run any power heads and the only other flow is moderate surface flow from my returnline.
I'll try to post a pic or two.
and a year later (I am slowly siphoning the substrate out to create a B.B.)
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Suzuki RV125