Whelk snails look like a nassarius snail. But there are differences this guy don't have the foot that the rest of my nassarius have. And I never see them on the sand really. Mostly on the rocks and glass.
Could you maybe get a picture of it flipped over and withdrawn? The answer would be a lot more definitive then. The top as shown in your picture is important, but the most important characteristics to IDing are on the other side.
Looks like a whelk to me. You can distinguish by the "tattoo" on the flesh of it. There's also something about the eyes, if memory serves. @Lionfish Lair should know for sure.
The shape of his opening and operculum. He does have a "door" right? In that last pic, it looks to have it's operculum closed? If there is no "door" there, I'm incorrect and it's not a whelk despite it having the other features of one.
I don't know how I got them. This tank as only been up for a yearor so and it used dry rock. So they had to be hitch hiker from corals or mixed in with snails when I bought some. I never bought these
Not really. Anything that would eat them, would eat more desirable snails as well. A lot of people have them in their tank and they don't know, so they don't kill off everything so that you would notice. Put some food in the tank, that should bring them out. I was just feeding my nassarius by hand and all I do is stick my hand in there with some salmon and they come running. I like feeling them take the food from me. I've had my snails a long time, some over 10 years.... I'm kinnda attached. LOL!