Do Pond Snails Have Spots?

[Kytkattin]

I have one snail in my 2 gallon that must have come in as an egg on the duckweed (it had a million things living in it! ) When I first put the duckweed in the tank there was no snail. Now, about 3-4 weeks later, there is a snail, but only one snail. First, I thought they would take over the tank, and much quicker than this if it is a pond snail. Second, upon closer inspection, the snail has spots on it's shell. Third, I doubt it will live long now that Spook is in the tank, she I just saw her attack it .

Any guesses as to what type of snail it is?