Back to the Basics: Breeding Guppies

Author: Maddy Hargrove

Many hobbyists began their fishkeeping with only a small and undemanding guppy tank, but they are hooked for life after seeing those small babies looking back out at them. A longtime aquarist offers a recap on guppy history, and the qualities that make them staples of the hobby.

Keeping Guppies as Kids and Adults

Many hobbyists began their adventure in fishkeeping as young children with the common guppy Poecilia reticulata. Many of these young hobbyists moved on to species harder to maintain and breed as they matured in the hobby. Oftentimes, their little aquatic friends from childhood were overlooked for many years. But due to their overall appeal, guppies can still be as exciting for us to breed and raise in adulthood, even if we have reached the apex of our fishkeeping skills.

It is never too late to begin breeding one of the neatest fish found in the aquarium trade. No other fish offers the brilliant colors, hardiness, ease of breeding, and beautiful physical display as the guppy does. When large numbers are mixed in a community tank with other peaceful species, the outcome can be simply stunning. The reasonable price for guppies in pet stores allows almost any fishkeeper, young or old, to become part of the fascinating world of one of our oldest friends.

Guppies are Social, Graceful Fish

Another reason that guppies have been very popular over the ages is their peaceful nature. Guppies make excellent community fish and are usually hardy enough to withstand the potential mistakes committed by the beginning hobbyist. Guppies are not known for their shyness—on the contrary, they can usually be found swimming flamboyantly in the open areas of the tank, an aspect that makes them a popular favorite among children.

The guppy is a fish the entire tropical fishkeeping hobby owes its popularity to. They have an extremely lengthy history and have been bred in the Americas for almost 100 years. Guppies still remain one of the least expensive and most plentiful of all tropical fishes.

Guppy History

The guppy is native to South America, including the islands of Barbados and Trinidad, and this wonderful little fish is bred commercially around the world. In the past, accidental escapes of guppies from commercial hatcheries allowed the guppy to greatly enlarge its wild habitats. As mentioned previously, the guppy is very hardy and will survive well in new waters, so they bred and multiplied quickly with little or no help.

The guppy’s common name was derived from Dr. Lechmere Guppy, who sent several specimens to the British Museum in 1866. The scientific name Poecilia reticulata was given to the species by an excited enthusiast named Wilhelm Peters in 1859 when he received his first Venezuelan shipment of guppies.

During the reign of the British Empire, guppies were purposely released into the tropics to eat mosquito larvae in an effort to reduce the high risk of malaria. Unfortunately, this was ineffective, and the guppies often upset the local ecosystem. At a later date, the mosquitofish Gambusia holbrooki was released instead. It was no more effective at controlling mosquitoes but was much more aggressive and has driven many native species almost to the point of extinction.

Physical Traits of Guppies

Wild guppies have little or no resemblance to their fancy captive-bred counterparts. The wild guppy strain is very small and quite dull in color. Females of this wild species tend to be brown or gray, with little or no coloring in the fin areas. The skin of these females is covered with black pigment cells called melanophores, which enable the wild guppies to rapidly change colors to avoid predators. While lying near a light sandy bottom, the guppy is able to quickly blend in with its surrounding environment. If the same fish were to move over an area of dark rocks, it would disperse black pigment to the cells to darken its color.

Female guppies grow to lengths of 2½ inches and begin breeding generally at an inch. Males reach lengths of 1½ inches on average—much smaller than the females. Males display various coloration patterns. Among captive bred strains, many lines have females with colored fins and partially colored bodies.

Guppies are bred for color, body size, and fin shape. Colors vary from strain to strain and include various types of solids and pastels. Tails come in a wide range of shapes and sizes including the lyretail (split-tail), the delta (fan shaped), thin (ribbon shaped), swords (single and double), and round. Hormones were once popular to artificially enhance the colors of guppies, but this often renders them sterile and is known to have caused changes in the secondary sex characteristics of the aquarists administering the drugs. Few if any breeders use hormones today.

Proper Aquarium Conditions

It comes as no surprise to anyone who has ever had the pleasure of owning guppies that they are able to live in a wide variety of water conditions, including fresh and salt water. Despite the fact that guppies are very forgiving of fluctuating water parameters, they should receive the finest conditions we can offer. Guppies should never be kept in small jars or bowls. Always choose the largest aquarium that your finances will allow. The proper temperature for the guppy is 72° to 78°F. The pH can be kept between 7.0 to 8.0. When you are ready to breed them, raise the temperature 2° to 3°F.

Guppies like having a handy hiding place or two, so you can make them very happy by building small openings with rocks, and then add a few spots of dense foliage accompanied by natural-looking gravel.

Guppy Breeding

Providing good water conditions, proper filtration, and a natural-looking environment will reward the hobbyist with years of enjoyable fishkeeping and spawning activity. Even when left on their own, guppies breed very rapidly. Therefore, consideration concerning future tank size and adequate filtration should be kept in mind. It is always wise to allow extra tank space for future guppy generations as well.


A rapid maturity rate is one reason guppies are very popular for breeding. Guppies are ovoviviparous and fertilize internally. The fry are born fully formed and are able to fend for themselves at birth, and the parents do not contribute to their needs afterwards. This lack of parental rearing seems to have no effect on the fry, who eagerly feed on their own as they rapidly grow toward maturity.


The anal fin of the male guppy develops into a sexual organ known as a gonopodium. This specialized and unique organ transfers sperm from the male to the female through her cloaca. The gonopodium is a result of the fusion of the third, fourth, and fifth rays of the anal fin. On the tip of the gonopodium are several small hooks that allow the male to hold on to the female during copulation.


The average brood for a female guppy ranges between 20 to 40 fry depending on the size of the female. Generally, the larger the female, the larger her brood. The world’s record for fry born in a single brood is held by a guppy at the Chicago Shedd Aquarium, who gave birth to 244 fry in one litter, of which 238 survived (Hemdal, 2003).

A unique feature among female guppies is their remarkable ability to give birth to several broods consecutively without male insemination occurring each time. This is possible because of special folds in the female’s genital area that store sperm until it is later needed for fertilization.

Selective Guppy Breeding

To prepare for selective breeding, the hobbyist first needs to choose several guppies with characteristics they believe can be intensified to produce true-breeding strains. These specific characteristics can include long fins, unusual coloration, and unique patterns. It is important to purchase a female of the same strain as the male you choose in order to strengthen the line and save valuable time, which can be better used in the pursuit of a new type of variation. While females do not show many traits that are visible on the males, they in part carry the genes for the expression of these traits.

A World of Possibility

Due to the fact that few strains are pure (producing identical fish from generation to generation), it is quite possible that you may end up with a new characteristic. New variations can occur through mutation as well. When it comes to the realm of breeding, nearly anything is possible.

Selecting Breeding Pairs

Both linebreeding and inbreeding are used to produce pure strains of guppies. The first step in this process is to choose a male and female with a number of similar characteristics you find interesting. If you do not want to just leave them to breed in your main tank, place a breeding pair together in a 10-gallon breeding tank containing a sponge filter and floating plants, which will give the fry hiding places directly after birth. Some guppy parents are cannibalistic and will devour their own young. The male should be removed before the fry are born, and the female should be removed right after the fry are born. Frequent water changes are vital to produce quality guppies.

Determining and Separating Sexes

Since a single insemination can produce a series of broods, it is best to separate the sexes as soon as possible so that you can control which males father the next generation of guppies. The new fry may be ready to reproduce in as little as three months in some cases. Early sexing can be accomplished by noting the distance of the anal fin from the pelvic fins. The female’s anal fin is set far back from the pelvic fin, while the male’s fin continually moves forward until it comes to rest between these fins at maturity.

It is easy to determine when a female is pregnant by her body shape. The female will get much larger and develop a gravid spot on her abdomen, which becomes darker and darker as birth nears. After birth, she will be ready to produce another brood in one month’s time.


Don’t be afraid to use inbreeding to fix your strain. A scientist in Denmark once inbred the same strain of guppies for a period of 24 years without the addition of any new blood. The end result of this experiment was a larger and stronger strain of guppies with no apparent damage or weakness caused by the inbreeding! If you do find your fish’s quality to be deteriorating, you can always outcross to another strain.

As new generations are born, keep an eye out for any males born with unique characteristics that can potentially be developed into new lines.

Feeding the Fry

Newborn fry should be fed newly hatched brine shrimp to ensure the greatest growth potential. Make sure to provide plenty of plants (rooted and floating) so the fry can hide until they have consumed enough food to increase their body size and avoid being eaten if you do not use a breeding tank.

Guppies are omnivores and prefer a diet consisting of both meat and vegetable matter. A well-rounded diet should include vegetable flakes, standard flakes, live brine shrimp, and live, frozen, and freeze-dried foods. Small offerings of boiled spinach or freshly chopped dark green lettuce will be appreciated as well.

Feeding should occur twice daily. Remove all food that has not been eaten over a period of five minutes. Remember that guppies have small mouths, so do not feed them any coarse foods. Guppies have a long gut and will generally eat only small amounts at a time.


Despite the fact that guppies are very hardy, pregnant females are susceptible to chilling, which can cause an outbreak of ich. The temperature in the breeding tank should remain between 78° and 80°F.

It does not require a great deal of expense or knowledge to breed and enjoy guppies in your home. Beginners and experts alike can enjoy the excitement of spawning one of our oldest and dearest aquatic companions. Guppies have remained a favorite for many years and will continue to do so for generations to come if we take the time to breed these beautiful, interesting, and marvelous creatures.


Hemdal, Jay F. 2003. Aquarium Fish Breeding. Barron’s Educational Series. Hauppauge, NY. 176 pp. D

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