If you think the terms "guppy" and "minnow" are interchangeable in most circumstances, you're wrong, but definitely not alone. The terms often describe any small fish with a length of about 2 inches or shorter. They're very different, however, but in most cases can live together in the same aquarium.
Guppies are native to South America, including Venezuela, Brazil, Guyanas and Barbados. They were introduced into other areas of the world, however, as a natural control for mosquito populations with limited success. Feral populations exist in Africa, the United Kingdom and various other countries. The minnow family, on the other hand, is native to several areas around the world, with about 230 of the 2,100 species occurring naturally in North American waters. Both are freshwater fish that inhabit a variety of different types of waters.
Just because their common names are sometimes used interchangeably doesn't mean these fishes look alike. Guppies possess long bodies with flowing, fanlike tails. They come in several colors in the aquarium trade, but wild males are much more colorful than their female counterparts. Minnows, on the other hand, are a large family; most aquarium minnows are gray to brown fish. Some variances occur, though, with the rosy-red fathead minnow's orange coloring serving as one example.
Both of these small fish do well in community aquariums with other species of docile fish. Minnows prefer water between 50 and 75 degrees Fahrenheit; guppies prefer a water temperature of 64 to 82 degrees. The pH should be around neutral or slightly higher for guppies and fatheads; research specific water requirements if you choose other types of minnows. Both are non-selective when it comes to food and will devour just about anything you put in the tank.
Due to its widespread use as a mosquito control agent, the guppy has had adverse effects on native fishes, including some types of minnow. They outcompete the small, native minnows for food and other resources. While it may seem hard to believe because "minnow" is normally used to describe any small, grayish fish, the largest members of the minnow family can grow to 100 pounds! Carp and goldfish are both members of the minnow family; goldfish are a far cry from the drab colors most often associated with this family of fishes.
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