Thousands of species of aquatic snails find their way into aquariums. Many species can thrive and breed under aquarium conditions. Aquariums snails either reproduce by laying eggs or giving birth to live young. Both types of reproduction can result in the snails overrunning a tank, which requires intervention.
Most aquarium snails reproduce by laying eggs. In general, aquarium snails lay clusters of jellylike eggs. Different species position their eggs in different places in the aquarium. For example, pond snails from the genera Physa and Physella usually lay their eggs above the waterline to avoid predation by fish. Some snail-eating fish -- like loaches -- will go out of their way to eat snail eggs in addition to preying on adult snails.
A few species of aquarium snail give birth to live young. These species reproduce slightly more quickly than their egg-laying cousins. One common livebearing snail is the Malaysian burrowing snail (Melanoides tuberculata). This species of snail has a cone-shaped shell and spends most of its time hiding in the aquarium substrate. Their offspring look like miniature versions of the adults. This species grows to about an inch in length.
Both livebearing and egg-laying snails can reproduce in great numbers, or bloom, under the right conditions. Even generally beneficial snails can overrun a tank if something goes wrong. Usually, overfeeding, or leaving dead fish or plants in a tank, provides extra nutrients to snails, which triggers a population explosion. These blooms can cause a number of problems. The extra snails put strain on the systems that keep the tanks healthy; they do this by producing waste and using up oxygen. Additionally, if the nutrients run out, the snails may all suddenly die and rot, damaging the water chemistry.
Controlling Snail Reproduction
You have several options to control snail populations. You can add 1 to 3 teaspoons of aquarium salt to the water. However, most aquarium plants and some fish cannot tolerate this amount of salt. Pet shops sell molluscicides, poisons designed to kill snails. Unfortunately, these products will often harm other critters in the tank, including fish. Some fish, like puffer fish and loaches, will eat snails readily but may have trouble getting along with other fish in the tank. The best way to control pest snails is prevention. To avoid introducing snails, dip any plants or decorations in potassium permanganate solutions and rinse them before adding them to aquariums.