I don't think it is a cerith or a nerite. Nerites have a more rounded shell from what I've seen, and cerith snails have a much more black pattern. It kind of reminds me of a cone snail, except the shell opening on a cone snail is from the side. And you probably would've lost a few inverts or small fish by now also (cone snails are venomous and only eat live foods, and will sting you too). If it's not bothering anything, then don't bother it for now IMO.