Kim Chance, age 8, of Enid, Oklahoma, for her question:

What do snails do in an aquarium?

Snails eat fresh green leaves and also scraps of decaying food. If we put certain snails into an aquarium, they devour all the floating, water weeds. This we do not want, because those plants provide oxygen and shade for the fishes. Besides, they look pretty. A pet shop has other water snails    and sow would rather eat scraps of decaying food or tiny specks of alga. These fellows do wonderful work in an aquarium.

They work as housekeepers to keep the place clean. As they crawl around the walls, they devour scraps of dirt on the glass. IJhen tiny algae multiply, they add a green cloud to the water. The right kind of water snail gobbles up the tiny alga before they get started. As you know, the fish strew a lot of food scraps through the water. The right snails devour these messy scraps before they have time to rot.