i have a mystery snail that my son wanted me to get for our tank, i relented and bought it and all has been wellfor 3 months, except the snail just died sat and i removed him sunday (i didnt know he was dead thought he was sleeping) so anyway i removed the snail and gag that thing smelled horrific, i was curious how long do snails live for and 2) i figured i should do a water change because i was afraid the snail might have released something into the water. was i right about changing the water? i did about a 30% change