Molly is the name of a group of small, colorful fish popular in home aquariums. Mollies are live-bearers—that is, they give birth to live, fully formed young. Most other fishes reproduce by laying eggs. Mollies are closely related to the guppy, another type of live-bearer.
Mollies are native to freshwater streams of South America, Central America, and the Southern United States. They sometimes enter pools and lagoons that have seawater mixed with fresh water. Adult mollies range in size from 3 to 6 inches (8 to 16 centimeters). Most species are naturally bluish or silvery-olive with various spots and bars. Male mollies are usually more colorful than females and have larger fins.
Favorite aquarium species include the Amazon molly, the sailfin molly, and the shortfin molly. Selective breeding has resulted in numerous colorful varieties of mollies that would not normally occur in nature.
