does live rock grow coral on it?

over time will my live rock grow any coral on it? i wont be adding my own coral to the tank tho.

 

Unless there is a hitchhiker on it (a hardy coral that was already on there), you won't get any coral. You will most likely get coralline algae growth witch is pretty cool and beneficial to your tank. It all depends on the proper lighting and water parameters.

 

Sometimes when you purchase live rock, it has spores and polyps and other good/bad hitch hikers. I had some live rock that grew some zoas, button polyps, and a gargonian. You never know!

 

You should be able to tell if your live rock is going to have random hitch hikers pop up. If your rock looks extremely natural and has odd colorations, or some random macro algae growth (which would indicate very little time out of the ocean) then you can expect a more diverse host of organisms to be housed in cracks and crevices.

On the other hand, if your rock looks fairly homogenous, with little color variations (or if it is just white or brown) then you can probably expect less.

I have seen live rock in my LFS that had giant multi colored sponges, covered in feather dusters, with halimeda and other types of macro algae still growing on it from the ocean. But as DanKistner said, this rock will invariably also have a higher likelihood to have harmful hitch hikers such as aiptasia or other pest anemones.

More and more people in the hobby are moving away from live rock and using base rock entirely and then seeding with a smaller piece of live rock. Hope this is/was helpful