Freshwater species are largely in the order Archaeogastropoda, within the subclass Prosobranchia, and feature an operculum and usually a spiral, coiled shell. Torsion is the developmental process that results in the rotation of the mantle and organs of the snail on its foot, creating the unusual and potentially undesirable positioning of the anus adjacent to the head and mouth. Although the larvae of aquatic snails are initially bilaterally symmetrical, little evidence remains in the asymmetric adult body form. Some species are distinguished from others on the basis of the direction of the shell coiling and body twisting as sinistral (left-handed) or dextral (right-handed). The well-developed eyes of aquatic snails are mounted on a pair of tentacles and connect to paired nerve bundles known as ganglia. Gastropods have a muscular foot that enables locomotion, which includes creeping, climbing, swimming, and burrowing. As the muscles of the foot ripple, a lubricating slime is secreted, helping the snail glide over any terrain.
Vernal pools have their own species of aquatic snails
Most aquatic snails are omnivores. That bodes well for your tank if you have live plants, because small pieces of dead plant matter often sink to the bottom of your tank. Like food, decaying plant matter produces ammonia. In most cases, snails will pick at the dead plant matter and leave live plants alone. Aquatic Community explains that the majority of snails aren't fans of certain poisons that live plants typically produce.
(Order) Aquatic Snails - Montana Field Guide
Freshwater snails can appear dead in aquariums, but they often just remain inactive for many days. Sometimes the snails float to the surface of the water due to the air in their lungs. If you suspect that the snail has died, you need to remove it from the water carefully to inspect it. Leaving a dead snail in an aquarium can result in the spread of disease. Before you discard the snail, inspect it carefully to ensure that it is actually dead and not inactive.
Order - Aquatic Snails - Basommatophora