Possibly. Maybe many of them do flutter off into the water, and some stay behind, stuck to the glass, I don't know. The egg capsules supposedly contain from around 40 to several hundred veligers each, potentially large enough for you to see with the naked eye. The little microshells included on the new veligers would be tiny though.
The third pic down on this link shows a veliger of Nassarius reticulatus. Is that what the new hatchlings look like in your tank?
http://www.sportesport.it/plancton06.htm
The article below looks to have some excellent info, but since you either have to pay a lot of money to access it or have a subscription (and I don't wanna, and don't have), I'll just have to go with the info included in the intro. In this day and age of cheap memory and broad internet access, it almost seems like an anachronism to have these companies store and charge so much for access to theses, dissertations, and journal excerpts. Maybe that will change soon, and everyone will have free access to the info included in these papers. But for now:
http://www.jstor.org/pss/1540388
Cheers,
Don