Correct me if I'm wrong here too, isn't the surface area of the rock more important than the pounds of the rock? SO due to this fact, I'm wondering about how much rock I need per gallon using volume instead of Pounds. My brother is getting a 125 gallon tank and I was going to have a sump 10g-20g tank filled with LR and then go to the skimmer then fuge then back to the tank. This will provide a larger area of just open water and better looking aquascaping in my eyes. For the sump I was going to use Fiji and for the display tank, I was going to mix it up with some super nice formed rocks to form caves and hiding areas. Here is one idea, why not fill the 1" baffles in sumps / fuges with LR rubble to help remove bubbles and provide filtration.