>Dear Andrew and Blue:-
>     I'm confused. You have mentioned dumping aquarium materials as
>the reason some species are in local rivers. It occurs to me that
>when people "dump" primarily water products, they do so down a
>toilet or a storm drain. The material then goes to a water
>purification plant which kills everything including bacteria before
>it is released into local rivers. How do snails survive this?

Hmmm... summa dem toilets in Redneckia may not connect to anything
much, just a ditch. Also kids, told to et rid of the snails, may be
soo soft-hearted to kill them...