Xiphophorus hellerii

Xiphophorus hellerii is a livebearing freshwater fish widely known as the green swordtail, distinguished by the elongated lower lobe of the male’s caudal fin that forms a sword-like extension. Native to streams and rivers of Central America, this species has become one of the classic aquarium fish because of its hardy nature, active swimming behavior, and the many colorful strains developed through selective breeding. When keeping Xiphophorus hellerii in captivity, providing ample swimming space, stable water conditions, and a balanced group structure is important for reducing aggression among males while supporting healthy growth and natural reproductive behavior.