Mosquitofish
The western mosquitofish can kill larger fish by biting their fins and eating their eggs and babies. It kills and eats smaller fish. It kills frogs by eating their eggs and tadpoles. After people put western mosquitofish in a body of water, there may be an algal bloom because the western mosquitofish kills all the fish that usually eat algae. The western mosquitofish is one reason why many other species are endangered. Some of the important ones are the Gila topminnow (Poeciliopsis occidentalis), and the damselfly in Hawaii.