
Apple snails have both a lung and a gill so yes, they can breathe underwater. If they have their siphons out though, they aren't really happy or the water isn't oxigenated enough.
They cannot have any fish to their Permanent needings
Tanks, first would cost too much, and not needed as the water creatures arent there permanently.
The water was yellowish and it smelled horrible
You should contact the manger or someone above him/her. Conditions should not be that way. the petsmarts(yes more then 1 :P) all have at least 10 gallon tanks for water animals, and their cages for birds and gerbils are big enough for the animals as well.but most of the PetSmarts I've seen keep 20+ decent sized brigs/diffusa in a medium size Kritter Keeper, which is usually then jammed in with their plants. There's no reason why they can't take a couple of their many 10 gallon tanks and put those same snails in there.
the petsmarts(yes more then 1 :P) all have at least 10 gallon tanks for water animals