Thanks, I knew the one at the back wasn't a nassaurius when it ate my other nassaurius, cerith, stomatella, trochus and saw it trying to eat this one. But never seen it so I wasn't able to get it out. I thought it was a whelk or some sort.
I'm certain the snail killer isn't a coral eater. It never ate any of my soft corals or any corals, had it for a long long time. Well I'm not sure about the Rapa being a coral eater too? I haven't introduced a large piece of rock or frag in a while, it's mostly coral frags on those plugs. So it's probably been there for a while. And like I said, none of my corals were eaten(eaten by nudi: yes). Anyway thanks! Got it out anyway, safer than sorry.