What asre those things called? I have a few very tiny ones (without the green center or middle dome) in my tank that came on a piece of LR from my LFS
I don't know what they are (I just call them polyps for lack of a better name) but they are about 1 inch tall, adn the top has a circle of small protrusions around it, much like the protrusions in the picture.
Also, the ones in my tank are almost the exact same color