Beneficial Snails
Nerite snails — algae eaters, do not reproduce in freshwater.
Mystery snails — peaceful cleaners, lay eggs above water line.
Malaysian trumpet snails — burrow and aerate substrate.
Pest Snails
Bladder and ramshorn snails — explosive reproduction in nutrient-heavy tanks.
Arrive as hitchhikers on plants.
Useful indicator of overfeeding.
Population Control
Reduce feeding.
Trap with lettuce leaf overnight, remove in morning.
Assassin snails eat other snails (they multiply slowly themselves).
Chemical treatments (copper) kill all invertebrates — last resort only.
Prevention
Quarantine new plants in bleach dip (1 part bleach 19 parts water, 2 minutes, rinse thoroughly).
Or hydrogen peroxide dip.