Guppies and minnows conjure an image of tiny fish, and generally they are both quite small -- but guppies and minnows are not very closely related. While they are hardy and share the ability to adapt to a variety of water types, salinity and temperatures, their differences are substantial.
Scientifically speaking, guppies and minnows are classified as separate families of fish. Guppies are in the Poeciliidae, or live bearing, family, while minnows are part of the Cyprinidae family. The common term "guppy" also refers to a specific order and class -- the Poecilia reticulata, to be exact. The commonly used term "minnow," on the other hand, refers to the large group of fish in the Cyprinidae family, such as carp, goldfish, chubs and shiners.
Guppies range in size from about 1.3 to 2.4 inches, with females growing larger than males. Minnows have a much wider range of size depending on the species. The majority of minnows are less than 4 inches in length, although the largest minnows, like carp, can average 14 inches long.
Female guppies aren't flashy and are usually a drab green or gray. Male guppies make up for this with a wide variety of bright colors and patterns, including red, orange, yellow, blue and green. Most minnows are a shiny silver, although some match their habitat with shades of dark green and brown. Goldfish and carp are the exceptions, and may be solid or spotted in shades of orange, red, yellow, white and black.
Native Range and Habitat
Guppies are native to tropical regions and are commonly imported from Trinidad and Tobago. They are also found in South America and the Caribbean. Since they originate in the tropics, guppies prefer warm water. Minnows are native to North America. They can be found across the continental United States. Since they are spread over such a diverse range, some minnows prefer cool temperatures while others thrive in warm water.
Guppies reproduce at a rapid rate, with each female capable of reproducing every 28 days, starting when she's 3 months old. They also bear live young who are well-developed at birth. Minnows deposit eggs in nests. The female usually guards the nest until the young hatch, although sometimes a male will take over this role.