Guppy ( Poecilia reticulata ) is one of the most common and popular aquarium fish; it is probably unlikely that pet shops that sell fish do not have them in their range. 

The Guppy, or Millionfish, as it is also called, may not be quite as popular as Goldfish; but, there is no doubt that it, together with a handful of other tropical aquarium fish, is the epitome of what an aquarium fish looks like.

Previously, the species was described as easily cultivated and durable, but nowadays, the general perception is that its popularity as an aquarium fish has made it commercially bred to an excessive extent, which has made it more susceptible to diseases and infections. 

Despite this, it is still a captivating and interesting fish for beginners and experienced enthusiasts, thanks to its decorative qualities and lively behavior. The fact that Guppy is also easy to grow and reproduce further contributes to their popularity.

Live Birth Carp

Guppy, along with some other common aquarium fish such as Platy, Molly and Swordbearer, belongs to a group called “live-bearing toothed carp” (Poeciliidae). 

What distinguishes the subgroup Poeciliinae in this family is, among other things, that they apparently give birth to fully developed fry; it is usually said that they are Ovovivipara. But, in fact, the eggs hatch just before birth in the female’s womb, where they have consumed their yolk sac.

In males, some strains of the anal fin have been transformed into a mating organ called the gonopodium. After fertilization, the female can store sperm, which means that she can give birth to several lots of fry without any further fertilization.

Species Description

Since the latter part of the 19th century, the species has been divided into six different genera (Poecilia, Lebistes, Girardinus, Heterandria, Acanthophacelus and Haridichthys) and assigned 12 different names. Still, since 1963 the generally accepted scientific name is Poecilia reticulata. Translated into English, the Latin name roughly means “variegated with mesh pattern.”

The popular name Guppy comes from the natural historian Robert John Lechmere Guppy (1836-1916), who worked in the Caribbean in the late 19th century and sent specimens from Trinidad to the Natural History Museum in London.

The Guppy is benthopelagic, which for aquarists means that it looks for food on the bottom, in the aquarium’s intermediate layer and at the water surface. In nature, it occurs in both freshwater and brackish water. 

Their natural habitat is the Caribbean and the northeastern parts of South America. There, they generally live in small warm streams and low-flow canals. 

In these places and in Asia, where they are grown, the water is somewhat alkaline. The vegetation is often dense but with a water surface reached by the sun.

Poecilia reticulata is an opportunistic species and is seen in places where it does not naturally occur but survives in the wild as an invasive species, especially in the United States and Australia. It is a known carrier of various parasites such as nematodes and trematodes and also attracts certain insect species.

A Guppy has an upward-pointing mouth, relatively large eyes and a rather characteristic elongated tail fin base. The males are about half as big as the females, which can reach a length of about two inches. 

The males show a much greater color splendor than the females, which are not infrequently (especially in nature), olive-colored with a silver-colored belly. Cultivated Guppy have a vast range of colors and patterns as well as fin varieties.

Guppy in the Aquarium

In aquariums, they are advantageously kept in shoals of five individuals or more, preferably with more females than males. 

The aquarium should not be less than 13 gallons and have a minimum length of about 20-24 inches. Guppies fit well in a traditional pet aquarium but avoid having them in the same aquarium as fin bites and keep in mind that their fry easily becomes food for cichlids and maze fish. 

For them to thrive well, there should be plenty of plants and free-swimming areas in the aquarium.

Their preference for alkaline water means that the pH should be between 7-8 with a water temperature of 71 °F – 78 °F, but they can withstand a few degrees warmer than that. A Guppy does not require any special feed, but some options are developed specifically for live feeders.

Growing Guppy

Growing a Guppy is just as easy or complex as you want to do it! Beginners will probably get guppy fry without any real effort, provided the aquarium is prosperous. If, on the other hand, you want to breed Guppy more seriously, you can contact any of the breeding associations or societies that exist via their websites or on social media.

If you are curious about breeding, there is some basic knowledge that you should keep in mind to maximize the chances that as many fry as possible will survive. With optimal conditions, it takes a little over three weeks from the moment of conception until the fry are born, but 4-5 weeks is more common. 

They are free-swimming right away, and this is lucky because the parents may try to eat them. An easy way to minimize the risk is to make at least sure that the fish are well-fed, or simply move the female before she gives birth to her own aquarium. 

After birth, the female is moved back, and the fry are allowed to grow up alone for the first two months. The young quickly become sexually mature, and already after a couple of months, you can see that the males develop nice colors.

The dark area at the genital opening becomes more prominent as the laying time approaches. A prerequisite for moving the fry to their own aquarium is, of course, that there is an aquarium with an existing bacterial flora to move to. 

The fastest and easiest way to solve that is to have an extra sponge filter or other inner filter in your regular aquarium that you can move to a smaller aquarium when the need arises. 

If it is not an option to move the fry to their own aquarium, their chances of surviving increase if the aquarium is well planted with, for example, floating plants. 

The fry are easy to take care of, and like to eat brine shrimp, for example. However, it is better to give them a regular complete feed for aquarium fish as long as the pieces are small enough.

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Karen Sanders

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