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Looks like green star polyps, one word about them they can over other corals so keep an eye out for that. I saw someone selling over 100 lbs of rock encrusted with green star polyps.
Yeah, looks like that to me. Many ways, I've had mine against the glass, it grew up and then I took it off like a rug and placed it on a rock. You can do the same method with another rock, then once it is spread enough, cut the two apart.