The western mosquitofish can kill larger fish by attacking their fins and eating their eggs and babies. It eats smaller fish. It likes to eat frog eggs and tadpoles. After people put western mosquitofish in a body of water, there may be an algal bloom because the western mosquitofish eats or kills all the fish that usually eat the algae. The western mosquitofish is one reason why many other species are endangered. Some of the important ones are the Railroad Valley springfish ("Crenichthys baileyi") in Nevada, the Sonoran topminnow ("Poeciliopsis occidentalis") in Arizona, and the damselfly in Hawaii.