Aquarium snails fall into three categories: beneficial workers, controllable populations, and pests. Beneficial workers: nerite snails (eat all algae types, won't reproduce in freshwater), mystery snails (peaceful, large, bright colors, won't multiply without male+female pair), Malaysian trumpet snails (aerate substrate, eat detritus, reproduce slowly). Controllable but breeders: ramshorn (eat algae + biofilm, multiply if overfed but easy to control via assassin snails or manual removal), Japanese trapdoor (cold-water specialist, livebearer, slow breeders). Pests: bladder snails + pond snails - small, hitchhike on plants, reproduce explosively when overfed. Not actually "harmful" but unsightly + outcompete other snails. Saltwater clean-up crew: trochus, cerith, nassarius, conch, astrea. Each species occupies a different niche. Predator solutions: assassin snails (Anentome helena) eat other snails - 5-6 will clear a 20-gallon of bladder snails in 4-8 weeks. Tank prep: dip new plants in 1:20 bleach for 60 seconds + rinse, or use a 5-min dip in 1L water + 1 tbsp alum. Prevents pest snail introduction.
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