270 gallon aquascape project

I am getting ready to set up a new tank and want to do a full background from live rock. The tank length is 9.5 feet. I have read various blogs of people using pond foam, egg crates and live rocks that is the direction I think I am going. My question is do I need to worry about water flow behind the rocks? I don't want to put all the time, effort and money into something that I will end up removing later on. Any info would be greatly appreciated!!