I've been wondering about mine too. I have dual returns and two oceanpulse duo powerheads?
It looks like everything blows around, they alternate every 6 minutes. I'm pretty sure I have dead spots behind my rocks. The top of the water does ripple.
It looks like the tank is still very lightly stocked, so it's not too late to take whatever measures you want to fix the detritus situation.
What are the tank's dimensions?
What about the pumps? Price looks nice, but while models do you have? Do they have the power to deliver significant flow to the front glass? From reading about them, you might be better off with side-placement so you can aim them directly at the front of your rocks.
If flow still isn't strong enough to keep detritus out of the back, you'll either need a supplemental pump back there, or to restack your rocks to allow more flow in back.