I am in the planning mode for a 90g tank. Why can't you use a combination of dead and live rock? For example build most of the reef with dead rock and add live rock in limited places. Won't the reef organisms spread to the dead rock and grow?
That's the way it's done. Piling LR on top of LR is a waste IMO. Use the base rock as a base and put you LR on top and in front. It will all be covered in coraline, sponge, and tubeworms in no time.use a combination of dead and live rock