When I worked at a lfs, my boss showed me a flyer he got from some husband/wife team in the Bahamas.
They had a live rock business going using lime rock I think, not quite sure though. They had 12 sites out in shallow water that they let seed for around a year. Then once a month they would go out and collect the rock from a site and replace it with new rock, ship out the old rock and kick back I guess till next month. What a life. I would like to do that for a living.
Here is another way:
<a href="http://www.athiel.com/lib10/rockmaking.htm" target="_blank">http://www.athiel.com/lib10/rockmaking.htm</a>