Fancy Guppy, Millions Fish

Family: Poeciliidae Guppies, Fancy Guppy, Poecilia reticulataFancy GuppiesPoecilia reticulataPhoto © Animal-World: Courtesy David Brough
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I have three male guppies in my tank and they are lovely beautiful fish. They don't bother any other fish in my tank and can someone tell me why one of my guppies... (more)  Connor

Fancy Guppies are the best known and most popular aquarium, and no two look the same!

Guppies Poecilia reticulata, also known as Millions Fish, are an all time favorite of both beginners and experienced fish keepers. The coloration is as individual as a fingerprint, making each specimen a unique work of art. Fancy varieties are exquisitely colored and sometimes have all the colors of the rainbow. Every Fancy Guppy is a masterpiece indeed, and no two fish are exactly alike!

This has been one of the most beloved fish species of the past century and has gotten many interested in the hobby. Dedicated breeders have managed in just a few decades to take the wild guppy, a mostly gray fish with a few splotches of color, and breed it into strains displaying the most intense and vibrant coloration imaginable. The Guppy packs a load of color for such a small fish, even the females who were comparatively drab until recently are being bred to show stunning tail coloration.

The appeal of the guppy is not only restricted to its gorgeous appearance, the personality of this fish has charmed generations of aquarists. The guppy is neither shy nor aggressive, its personality is characterized by a wonderful balance of activity and confidence.

Something to be wary of with this species is stock quality. Mass produced stock that is of low quality will be disease ridden. These fish are unfortunately rather prone to fungal infections which can easily damage the tissue of the Guppy's large tail. Another problem related to the stock quality is that some of the fanciest true breeding strains of guppies will be highly inbred. This leads to genetic weaknesses that can also decrease hardiness and resistance.

What's in the name?
Poecilia means "many-colored"
reticulata means "netlike"

Overall they are very tolerant of a wide variety of tank conditions, though the highly inbred specialized species can be more delicate and require more attention. A tank with some plants and 1 to 1.25 teaspoons of aquarium salt per gallon will keep this beautiful little fish happy and healthy. They are capable of adapting to brackish or saltwater conditions.

This fish is probably the most widely available species of tropical fish. As the common name Millions Fish suggests, this species breeds readily and frequently. The aquarist that chooses to keep fish of both genders will soon have a tank with multiple generations of Guppy in their aquarium.

For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care

Geographic Distribution
Poecilia reticulata
Data provided by
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Cyprinodontiformes
  • Family: Poeciliidae
  • Genus: Poecilia
  • Species: reticulata
Guppies - Millions Fish

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Guppies, good for beginners and all aquarists

Guppies are fun and great to own. They come in all sorts of colors and are easy to care for and breed.

Fancy Guppies - Quick Aquarium Care
  • Aquarist Experience Level: Beginner
  • Size of fish - inches: 2.4 inches (5.99 cm)
  • Minimum Tank Size: 5 gal (19 L)
  • Temperament: Peaceful
  • Aquarium Hardiness: Very Hardy
  • Temperature: 68.0 to 82.0° F (20.0 to 27.8° C)
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Habitat: Distribution / Background

The Guppy Poecilia reticulata was described by Wilhem Peters in 1859. They are widely distributed in Southern and Central America, specifically Venezuela, Barbados, Trinidad, Brazil and the Guyanas. They have been introduced to a wider range within the Americas and Australia, mostly for mosquito control. They are not endangered and the Guppy is not listed on the IUCN Red list of Threatened Species.

Specimens collected by the botanist Dr. Robert Guppy in 1866 were brought to Europe, and they were determined to be a new species by the British Museum. The species was named after Dr. Guppy. Other common names they are known by are Millions Fish, Million Fish, Fancy Guppy, Ornamental Guppy, Rainbow Fish, and Fancy Millions Fish Guppy.

There is a great deal of color diversity within the species and it breeds readily, and in a short amount of time. These characteristics have made it possible for the hobby to create an incredible variety of strains with all kinds of color combinations and patterns. There is also a diverse range of variations in the tail fin including Sword and Double sword varieties, Roundtail, Pintail, Flagtail and the ever popular Fantail variety.

In the wild Guppies are found in a very wide range of water bodies including canals, ditches, warm springs, turbid ponds, and mountain streams. They occur in a wide variety of habitats, but are usually found in waters that are quiet and densely vegetated. They can tolerate a wide salinity range and water temperatures ranging from 64-82° F (18-28° C). These fish often live in shoals in the wild, varying with the amount of predation.They feed on detritus with algae and plant matter and also consume zooplankton, diatoms, invertebrates, small insects, and insect larvae.

  • Scientific Name: Poecilia reticulata
  • Social Grouping: Groups - Though not a schooling fish they will often shoal in the wild, varying with the amount of predation.
  • IUCN Red List: NE - Not Evaluated or not listed


The Guppy is a small fish with an elongated body. Along with the Mollies, Swordtails and Platy fish, it is a member of the Poeciliidae family of Live-bearing Toothcarps, which are distinguished by having teeth in both their upper and lower jaws. Females are larger, reaching between 1.2 to 2.4 inches (3-6 cm) in length while the males reach between .6 to 1.4 inches (3-6 cm). Fancy Guppies produced in captivity can get a bit larger than their wild relatives.

Male Fantail Guppy
Male Fantail Guppy

Their lifespan in the wild is quite variable but averages about 2 years. A well cared for aquarium guppy lives 1 1/2 to 3 years on average, having the shorter lifespan if kept in warmer water which speeds their metabolism.

Guppy males are smaller and more slender, and have all sorts of colors. The larger females are a lead gray color. Males usually have a larger more colorful tail fin than females as well. As the male fish matures, the middle rays of its anal fin become modified into a narrow copulatory organ called a gonopodium.

There are fancy guppy organizations that breed and show guppies all over the world. Selectively bred Guppies come in all colors and combinations of colors. It can be said that they come in every color of the rainbow, and often have every color of the rainbow in them!

Female Fantail Guppy
Female Fantail Guppy

Colors play an important role in selective breeding. They start with a ground color (main upper body color) that is marked with a "cover" (primarily on the lower body) of bright iridescent colorings and patterns.

There are 4 basic ground colors (wild-color, albino, blond, and blue) as well as a number of other ground colors developed with combinations of those four. The cover can be any imaginable color or combination of colors, and are given a variety of different names. Some pattern examples are snakeskin (rosette, chain-link pattern), carpet, cobra (rosette pattern with vertical bars), and black (called "tux" or "half-blacks").

Selectively bred Guppies also have a large variety of tail fins. There are 12 different standard shapes recognized by breeders of Fancy Guppies including round-tail, pintail, pointed or spear-tail, swordtail (double sword, top sword, and bottom sword), lyretail, spadetail, flagtail, veiltail, fantail, and triangletail or delta. Guppies are named by the color of the tail, so if it has a yellow body but a red tail, it will be called a red guppy.

  • Size of fish - inches: 2.4 inches (5.99 cm) - Females are larger, with males about 1/2 the size. Although the common length is only about 1.1" (2.8 cm) captive guppies can grow larger.
  • Lifespan: 2 years - On average these fish will about 2 years, both in the wild and in captivity, but well cared for captive specimens can live even longer, up to about 3 years.

Fish Keeping Difficulty

The Guppy is remarkably easy to care for and to breed. Its generally very hardy and undemanding, making it a perfect choice for the beginning aquarist. Being less demanding of water quality than most other fish, having a wide tolerance for water temperature, it is rarely ill.

Make sure you select only healthy fish and provide a good tank and varied diet to offset any potential problems. This fish is very widely available, however there is a great disparity in the quality of stock. The extensive finnage of this species also makes it susceptible to damage which can result in infection.

  • Aquarium Hardiness: Very Hardy - Guppies are very durable, but there is a disparity in the quality of available stock, and extensive finnage is susceptible to damage and resulting infection.
  • Aquarist Experience Level: Beginner

Foods and Feeding

Since they are omnivorous, the Guppy will generally eat all kinds of fresh, frozen, and flake foods. In the wild their diet consists of detritus with algae and plant matter, zooplankton, diatoms, invertebrates, small insects, and insect larvae.

In the aquarium they will gladly eat most commercially prepared fish foods as well as supplementary live and vegetable based food. Feed brine shrimp (either live or frozen) or blood worms as a treat. Baby brine shrimp are a favorite of this species. This fish is not a picky eater but should be fed a varied diet several times daily, in very small amounts.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day - Feed small amounts several times a day, what the fish can consume in about 3 minutes each time.

Aquarium Care

The Guppy does not require special aquarium care and are not too demanding about their tank. Still the tank should have regular water changes of 25% two to three times a month. It will need more or less depending how many fish there are and the condition of the water.

As with most of this family, it is also advisable to add 1-1.25 teaspoons of aquarium salt per gallon. Be sure to only replace water with salted water if that is what was from the tank. Water which evaporates will leave salts behind, so there is no need to add more salt if you are topping off evaporated water.

  • Water Changes: Bi-weekly - Do water changes of 25% every 2-3 weeks, more often with heavily stocked tanks.

Aquarium Setup

The small but active guppy requires little to be happy. A 5 gallon tank is large enough to keep a trio guppies. Generally the genders are mixed however, and so the aquarist should plan for frequent breeding with a potentially great deal of resultant offspring. A 10 to 20 gallon tank may soon be needed. It is best if females outpopulate males slightly to reduce competitive squabbles between males.

These fish will appreciate an aquarium with fine gravel that is heavily planted along with some floating ferns. This type of vegetation will provide a bit of food for them as well as hiding places for the fry until they are large enough to not be eaten. Any lighting, dim to bright, is fine, but if the light is excessively high from above it tends to wash out their coloration.

Most Guppies are very tolerant of a wide variety of tank conditions, though the highly inbred specialized species can be more delicate and require more attention. Although they are very tolerant of water conditions, good filtration is very helpful in maintaining stable water. Filtration systems remove much of the detritus, excess foods and waste. This in turn helps to keep the tank clean and maintain the general health of the fish.

  • Minimum Tank Size: 5 gal (19 L) - A trio can be kept in a 5 gallon (18 Liters) tank, but keeping mixed sexes will result in breeding and quickly increase the population, and then a larger tank may be needed.
  • Suitable for Nano Tank: Yes
  • Substrate Type: Small Gravel
  • Lighting Needs: Moderate - normal lighting - This fish tolerates low to high lighting, although excessively high lighting from above tends to wash out their coloration.
  • Temperature: 68.0 to 82.0° F (20.0 to 27.8° C)
  • Range ph: 6.8-8.5
  • Hardness Range: 10 - 28 dGH
  • Brackish: No - This is not a brackish water fish, but it does appreciate a little salt in the water of about 1-1.25 teaspoon per gallon of water.
  • Water Movement: Weak - Water movement should be weak to moderate.
  • Water Region: All - The Guppy swims in all levels of the aquarium.

Social Behaviors

The Guppy is extremely active but also very friendly. This fish has a very kind and even temperament, and is generally peaceful and active. This sociable fish combines well with all good natured fish. Small fishes such as armored catfish (Corydoras), Platy fish, Tetras and other Characins make good tankmates.

These active fish form loose schools and are always on the move. Though they are peaceful community fish and easily kept with other livebearers, they may chase fry and will often nip the fins of the Betta or Siamese Fighting Fish. So the second thing which the aquarist should avoid is combining the Guppy with the Betta, particularly in small quarters, as one of the two or both are bound to get their fins shredded eventually.

  • Venomous: No
  • Temperament: Peaceful - This is an excellent community fish and mixes well with most other small peaceful fish. The exception to this is the Betta fish, which will either suffer fin nipping by the guppy or mistake guppies for another Betta and will attack. In either case, this combination does not usually end well.
  • Compatible with:
    • Same species - conspecifics: Yes - They are tolerant of juveniles, but they will chase and eat newborn fry.
    • Peaceful fish (): Safe
    • Semi-Aggressive (): Monitor
    • Semi-Aggressive (): Monitor
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Slow Swimmers & Eaters (): Safe
    • Shrimps, Crabs, Snails: Safe - not aggressive
    • Plants: Safe

Sex: Sexual differences

The female guppy is both longer and stockier, and tends to have less rich coloration. Females may also have a spawning patch, a small dark blotch at the base of the caudal fin, at breeding time. The male Guppy is smaller and slender, and will generally have a longer more colorful tail fin. The male also has a gonopodium, a modification of the anal fin into a rod shape which is used in the reproductive process.

Breeding / Reproduction

This live-bearing fish breeds readily in the home aquarium without special attention if well fed and cared for. Little more is required than to introduce both genders into the aquarium. The young reach sexual maturity at a very young age. Males mature in 7 weeks or less and females at 3 months of age.

To selectively breed guppies, you will want to have on male with two or three females. Provide a breeding tank that is 10 to 20 gallons in size with gentle filtration. You will notice the female is pregnant when she develops a gravid spot, a dark mark on her abdomen. The gestation period is about 26 to 31 days.

Monitor the fish closely when she is close to giving live birth. Guppies will chase their fry and may eat them if given a chance. The young will be consumed unless they are removed, isolated as with a breeding trap for example, or simply given enough hiding spaces such as dense rooted or floating plants. The broods can be up to 100 fry, and the female can produce young again in about four to eight weeks. For more information, see the guide for breeding Livebearing Fish: Breeding Freshwater Fish - Livebearers.

  • Ease of Breeding: Easy

Fish Diseases

The Guppies are relatively hardy and do not have any particularly strong weaknesses for certain diseases, though their extensive fins can fall victim to fungal infections. Still they are subject to the same diseases as other tropical fish. One of the most common freshwater fish ailments is ich. The best way to proactively prevent disease is to give them the proper environment and give them a well balanced diet. The closer to their natural habitat the less stress the fish will have, making them healthier and happy. A stressed fish is more likely to acquire disease.

Anything you add to your tank can bring disease to your tank. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so not to upset the balance. For information about fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.


The Guppy is among the most commonly available fish is the world, usually at a very modest price.


Author: Clarice Brough CFS, Barbara Roth
Lastest Animal Stories on Fancy Guppies

Connor - 2014-11-23
I have three male guppies in my tank and they are lovely beautiful fish. They don't bother any other fish in my tank and can someone tell me why one of my guppies goes to the bottom of the tank every night to sleep and when he wakes up he doesn't look good and then after eats fine and swims perfectly like they should. But they are lovely fish to keep so I recommend you get some.

fish bandit - 2013-11-03
Why isn't there much about endlers on this site? They are colorful live bearers like guppies and mollies... anyway does anyone raise/breed freshwater shrimp? They are great in a tank with some otos, endlers, and some guppies.

  • Clarice Brough - 2013-11-07
    Glad you asked as we have the Endler Guppie in the que for adding. Hopefully we'll get it live soon, so keep an eye out:) I also would like to know of anyone who raises freshwater shrimp, so look forward to some info on that.
Anonymous - 2012-08-14
Can a cross between a guppy (female)and a molly (male) be made as I have a single guppy in my tank I thought to get 2 male mollys as my female guppy is large and allmost size of the molly males

Anonymous - 2013-08-02
This is gonna sound kinda funny but my guppy is fat. It's a male so not prego for sure but I have another and it is waaaay slimmer than this one. They are both the same size in length but the others girth is far larger. And they eat the same amount whenever I am there. This isn't a new occurrence, it has always been like this and it seems healthy but it is almost annoying at this point. Does anyone else have an overweight guppy that can't shed the pounds?