Hi all, I've got a 58 gal with 5 "Nassarius" snails. They stay in/on the sandbed except during feeding. They emerge, and zoom all over, including glass and rock, trying to get food. On two different feeding occasions, I watched a "Nass" take a perfectly healthy trochus right off the glass and eat it, the other time, a cerith. I've also got 2 ceriths rolled over, not yet dead, but not doing well, I am suspicious the "Nass" are to blame, although they haven't finished them off, which is weird.
Evidence for Nass:
Fast
Buries in DSB
Scavenges - have seen them eat known dead/dying snails that they did not attack. (I acclimated some poorly once and had high mortality)
Evidence for Whelk:
While it doesn't visually perfectly match either mollusk in the link, it's closer to whelk
Attacking other snails that, as far as I can tell, were healthy.
Has operculum
I am thinking of taking these back to the LFS who sold me them, they have been really good and should know better if these are whelks.