come to think of it, i had a few nerites in with my rams and they have since turned up as empty shells. You might be on to something there.
I collected a group of about 50 nerites from a brackish area and put them directly into FW. Nearly all survived the trip and transition, and I since moved them throughout different tanks to get an idea of their longevity and behavior.
In the tanks with guppies, they are all doing fine. In the tank with the discus and angelfish, they are all still there and moving around just fine. In the tank with golden topminnows, they appear to be doing o.k., although a few have turned up empty. In the ram/black cory tank, the few that were in there are now empty, however I do see a large ramshorn in there from time to time, but they never have a real population boom.
And finally, in my native pygmy sunfish/least killifish/pygmy killifish tank, they seem to be thriving. The tank is heavily planted, and while I occasionally see eggs, they are short lived since the pygmy sunfish seem to relish them.