Why do experts advise keeping mollusks, such as pond snails, in an aquarium?

This advice is most useful for inexperienced aquarists.

At first, they can put much more food for the fish than is required, because of which the excess food settles to the bottom and begins to decompose, polluting the water, in addition, bacteria grow in them. Also fish can overeat.

To prevent this from happening, they give birth to snails. They quickly eat up the remains of food for the fish, preventing it from accumulating. Also, snails reproduce quickly, and fish can feed on small individuals.

In addition, the snails eat the vegetation, clearing the aquarium of decaying algae.