I really don't think it's caulerpa. I have the leafy and grape variety all over my live rock. What a pain! And this is really different. There are no vine like strands and it grew out of the red velvety growth on the live rock.
Some sort of macroalgae. I have a something almost like that and it grows out in long strands and branches and I have to pluck it off like once a month. It really isn't a big deal. A tang would probably make a quick meal out of it.
:joy:
