Its a lovely small colony and i hate to quell your excitement but that is not a Rhizo. Its a Eguchipsammia fistula (often referred to incorrectly as dendrophyllia fistula). Common names are Orange cup coral, fat head dendro's, firecracker coral, Orange Sun Coral.
Rhizo's grow in a singular clam shell and the indivdual heads are much larger. I have thread on here with a number of images of Rhizo's.