I also have a 12" high tank. I have found that keeping coral in the lower half and haveing wide current in the water column above them (a tunze or similiar for your size tank) and direct/high velocity flow shooting at the bottom so that it can bounce off (not possible with sand) makes the entire water column move in a wide steady flow. Polyps should be swaying and not just blowing in one direction. A unobstructed water column above rocks is much easier to produce eaven water movement in than trying to blow water around rocks. two streams/modded maxi-jets (streams ideally) aimed across the top of the water column from the two rear corners to opposite front corners will give very even/thorough flow, as long as the focus of the water-stream is not obstructed by rock. Keep the coral in the lower half of the tank below this flow and it will give them time to grow/adapt into it. The portion of the flow that hits the other side of the tank (opposite the streams) will roll down the glass and curl under, if you have sand this may be an issue, if you are bb this works out great as it blows under the corals. This is not a BB/SB good/bad thing, just something to think about, especially in a shallow tank where you do not have a deep water column to absorb the flow that bounces off the glass.
Sometimes re-arranging rock does more than adding more ph's (not saying this is your current issue)
-John-
