I had a small snail (about 1" / 2.5 cm shell) in the same tank as my betta fish. They seemed to both be doing fine living together for the 7 months I've had them. But this week, I checked up on the tank and found the snail shell overturned. I tried flipping it upright but when I looked later it was flipped over again and looked empty, which is sad.
I had changed the filter and added water recently (2-3 weeks ago), but I've done water changes in the past and the snail was fine, so I don't see why it would have hurt the snail this time.
Do betta fish attack snails, and if so, why might it have done now? Or did the snail probably die of other causes?