So I am still in the process of setting up my 100 gal reef tank. I ordered some live rock today. Pretty good price. Fiji standard for 3.35 a lb shipped overnight (this includes the shipping cost) Unfortunately even with the price I could not afford to get as much as I wanted. What kind of rock can I use to put under the live rock that will eventually turn to live rock as well. Could I use lava rock or something similar that is porous yet significantly cheaper than even what I was able to find for live rock? I would like to find a couple of big pieces of something that I can stack the live rock on top of.