You need to make sure your going from big to small going from the back to front.
[/COLOR]What you mainly want to achieve is to have a main rock structure and push it more towards the back of the tank. In my opinion, it’s always good to leave room behind the rock so you can clean the glass especially on clear background tanks. Build off that main structure. Add a peak and have it slope down. Go from big to small and moving the rocks closer to the front. You do not want a straight line or bigger to smaller rocks though. Again you want it to look composed. Make it have a slight curve towards the center of to tank. You can have one big rock work towards the back and have a medium on the opposite side of the thirds point, having the medium rock more center/foreword. Congratulations, you just created DOF! I like to have some small rocks almost right up the the front of the glass. When all is said and done you should have a back ground structure, a mid (whether it be a coral or a medium rock) to the Forward structure. You need to make sure your going from big to small going from the back to front. I hope that makes sense.