Mosquito fish serve a very useful function in a pond. They eat the larvae of mosquitoes that grow in the pond when they come to the surface of the pond to get air. This reduces the number of biting and disease-carrying mosquitoes that emerge from the pond. The larger bluegill eat the smaller mosquitofish as well as other animals of the right size, such as baby fish, frogs, worms, and insects. A largemouth bass will eat the smaller bluegill and anything else that is smaller than it.
Carnivores keep the smaller animals from becoming too numerous and crowding the pond.
Other, more advanced, plants live in the pond. One of these is a flowering plant called Elodea that is often used to decorate freshwater aquaria. Elodea has its roots in the mud of shallow streams and ponds and grows in long leafy branches. Another water plant is a frilly-leafed plant called fanwort . Both of these plants provide a place to live for attached algae and small animals like snails and insect larvae.