Yes, it allows for room to grow coraline algae, but that is not the main purpose of using "live rock". All foam provides is a solid object to take up space in the tank and create a surface for other things to grow on or be placed on. It is not "live" and does not aid in the filtration of the tank water as "live rock" does. That was my point to the original poster, to not think that by using foam that he would get the same benefits of using real live rock.