Originally Posted by S_Hurley
So basically these things grow on live rocks?
Yes. The live rock is brought in straight from the ocean. So there are hundreds of things living in it. I've identified aiptasia, pineapple sponges, asterina starfish, and tube worms growing from mine, but there is a lot of stuff in there that's growing that I don't know what it is. Most of the stuff is filter feeders and not bad for the tank. And the live rock will provide plenty of bacteria that filters water and also provides food for any starfish, snails, or crabs you might get.