I'm looking for some ideas or things that you guys have looked back on a went "Ohh man I wish I would have done that!!"

One thing that I am thinking about is putting a power head near the center of the tank but need some ideas on how to hide the wire coming down the back of the tank inside. I'm already doing a rock wall but do I want to put it behind the rock wall (the wire) and then what happens if I need to remove the power head...? Yeah not a good idea.

Thanks in advance for any ideas.