Looks like a scavenging snail called a Auger snail. Definitely not a cerith snail. Where did you find it? in the sand? live rock? Family Terebridae. terebre genus?
This snail is very new, probally was larvae a month ago. Either came in on something you introduced or it was born in your tank. Looks like a herbivorous snail. I notice its cleaning with its radula. Most likley it's safe, but not 100%. At this stage its hard to tell what genus its from. It...