Where to place duelling powerheads?

[leafyseadragon]

I have one powerhead in my tank right now, and I can see there are some dead spots in the water flow. Another powerhead is in the mail.

From looking at other posts it seems the best place to position powerheads for maximum turbulence is on opposite sides of the tank, so that their flow forms an "X" when viewed from above.

But I have a large pile of rock in the middle of my tank, and it's piled fairly high. Should I still angle the powerheads to form an "X," even if the flow is pointing right at my LR? Or should I put the powerheads right near the water's surface? In general, does it matter how high I place the powerhead: low near the sand, or high near the water's surface?

BTW, just put 10 blue-leg hermits in my tank Friday. It's "Where's Waldo?" in there now. I've only refound three of them.

 

[biotoxin]

you want the top water to be somewhat turbulent for the gas/air exchange to occur. As far as it forming an x thats just to cover all the dead spots. I have 2 ph's and one is in the top left corner and the other one is bottom right so they work together and keep the flow constant.