Just saw this today growing on my rock with green star polyps that i got 3 days ago. Whatever it is, is there anyway i can move it to stop the gsp from over running it?
Looks like a paly (?) but i would wait for it to get a little bit bigger (it might not) and then cut it at the base of the stock and move it to where you want it to go.
You have some time, the GSP wont grow over it overnight.