Typically you might find it as
Clavularia sp., thought I've seen some places advertise it as Sansibia sp. I'm not sure which it is, but either way I've never found a species name.
It grows extremely fast and I've found little patches all over my tank. It just seems to pop up out of nowhere. I think it might be because I've fragged my colony above the water and the rotary tool chopped up tiny pieces and the water flow scattered them all over. There's got to be at least a dozen patches growing where I didn't intentionally plant it. Good coral to fill up small empty spaces.
A lot of the LFS around me gets these in once in a while. You can ask around your LFS or I have some for sale if you can't find any locally. Shipping would be a killer though.
lol nice one coach