Index Of /bilder Kates How Long Do Water Snails Live?

How long do water snails live? - index of /bilder kates

I have two snails, 31 / 4 years! They are much like the worm http://garnele-online.de/bilder/Clithonb ... only without the horns on the shell. If the link does not work, are very small, brown, size of the nail of my index and fresh water. I have had a school project, I do not know what type they are.
Thank you!