Guys if they are cerith snails jump on Dave's offer, I just dumped 4 dozen in my new tank and they are excellent cleaners. And they are most active at night when the lights are out.
I also added 100 astrea's, and some nerite 's as well. Almost all of the nasties from curing my rock are gone in a week since I added them.
The cerith snails have a long black pointed conical shell adults, are around an inch or so long.
Kevin