I think with enough time. That is the problem for most people. The thing I like about live rock is all the holes predrilled by critters and enough seem to survive to repopulate the rock. I guess 1/3 base rock I think its called (reef bones) 2/3 live rock would work out ok. Just would take longer to get the full benifit.
I have some lace rock that Im not using anymore that you can have for free... There's a post on the equipment for sale I think with a picture of it. One of the LFS sells it for like $2/lb... I know coraline algae will grow on it, but Im not sure if critters can grow in it. Might want to google it a bit.
Yes as everyone has already said on the base rock becoming live.
Might I suggest that you check out Under the Sea in Mt Vernon off Kenkaid exit and two or three blocks down to 1st St. He has dead reef rock thats in a live rock tank that already has been seeded for about 2.00 a pound last time I was there and bought some and I doubt the price has changes much if any since. I picked up about 35 lbs of what essebntail would have been Tonga Branch shaped pieces and two months later its looking quiet live with only the addition of 2 lbs of Live Tonga Branch rock in that tank! He also has pieces of whats the equivelent on Fiji for the same price! This is much better than Lace Rock and is a steal compared to what you can get "locally" in your area.
I was using Lace rock until Under the Sea opened back up and this time in a real store front! The Lace rock is okay and its great for making ledges, but it doesnt compare remotely to the "dead reef rock" Nathan is selling at his store. Its a small quaint little shop and there prices are so cheap it should be against the law! At least stop in and check them out. Good people and good little store with a lot of potential in the future.