Thats part of the planning that should go into the set-up of your tank. Some stack their rocks, others glue, but keep them about 2 inches from back pane, and other glue base rocks, and stack upper levels for easy manipulations. Just depends on how you plan to arrange it, the space you have to work with, and how good of circulation you plan to have. In addition to making sure you have powerful powerheads on your side, there are also small submersible ones which take up only a few inches, and can be suction cupped to the glass, or some even use a mag. where one side is on the outside, and the other, in the tank. These little suckers are actually pretty powerful, and usually only require a single cord, and it's very thin, so easy to hide. I have two in my smaller 29 reef, and they are placed on opposite sides of the tank, and in the middle there is a cove left open, so the debris is blown towards the middle in the cove, and once it starts floating, either my dual bio filter or protein skimmer grabs it, as those intakes are located right above that area.