Live rock is a fantastic tool to use as a method of filtration in the saltwater aquarium. Another good thing about live rock is that it looks so natural in the aquarium.
There are a couple of issues however:
1. Live rock, dependant upon the amount required is not that cheap
2. You never quite get the shapes and sizes you need to create the rock structure you hoped for.
For these reasons and some others which I have not mentioned there are some people in this hobby who are now looking at making their own live rock.