These are barnacles and harmless. We see theses on wild caught or mariculture corals. They will starve after sometime in our tank since they often will not be able to catch enough food.
On the side note, you gonipora seem to be receding from the base. I would put it on top of a piece of flat rock so that the sand does not cover the lower polyps and hope for the best. Often wild caught and mariculture goni will just whittle away
He mean the Goniopora. I agree.+1. IMO it's a goner.