Could this be a vermeil snail? It is on only one coral (SOLAR FLARE) have removed a couple of times even took toothbrush to area but comes back. It is not a polyp. My next thought is to cut tip off coral but hate to do that.
It does not appear to be a vermetid snail to me, but the photo is blurry when I zoom in. Can you get a clearer pic? It appears to be on both branches, yes?