Thanks, y'all. Those are some tiny eggs. I was fairly surprised to find that they spend at least a little time in the plankton as they reproduce pretty well. Jonathan, you might be surprised to hear that my population seems to be waning, though. I think the collumbellids are out competing them in the display. I just moved a small population of ceriths to a new tank that's never seen snails, though. So maybe they'll perk up again. I think that they just over-populated the tank in my system where they've been most successful, and so stopped putting down egg masses in there. I'm also now feeding that tank more to get more nutrients in there. I need to start exporting collumbellids to the fish store or something.