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The Guppy – Poecilia reticulata

Wild Guppies

The Guppy is amongst the most popular of freshwater aquarium fishes, particularly for beginners.

The Guppy is resilient, easy to keep, is easy to breed and comes in a wide range of colours. Being a livebearer, it is an ideal fish for novice aquarists to breed successfully.


The Guppy was first documented in 1859 in Venezuela and in 1861 in Barbados. In addition, they are native to Antigua and Barbuda, Brazil, Guyana, Jamaica, parts of the Antilles, parts of the Virgin Islands and Trinidad and Tobago. Guppies have also been successfully introduced widely in tropical and sub-tropical regions and are unusual in that they can survive and thrive successfully both in freshwater and saltwater.


The Guppy has a typical lifespan of around two years. Males vary in size between just over 0.5″ to around 1.5″ whilst the larger females vary in size from around 1.2″ to 2.4″.

Being livebearers, the male has a modified anal fin called a “gonopodium” through which (by consent or otherwise) it will pass spermatozoa into the female’s genital pore.

The female can be fertilized by more than one male at the same time (known as “polyandry”) and, interestingly, the sperm from males can be stored within the female long after the male has died such that new eggs can be fertilized by the sperm of a long-dead male.

In the wild, the female guppy will seek to mate with males displaying orange spots on their sides. Such spots are present when the male can successfully forage for carotenoids which it would find in the orange fruits of Cabrehash trees. This quest for a more colourful male mate has, in captivity, lead to increasingly elaborate colouration and fancy tails in males.

Fantail Guppy
Female Guppy on the left – male Fantail Guppy on the right.

Guppies are, by nature, a shoal fish, as this characteristic offers better protection from predation. In the aquarium, it is generally felt wise to maintain guppies in sufficient numbers to permit them to shoal.


Guppies are excellent “browsers” in the aquarium and will feed off algae, plant material as well as any live food present in the tank (e.g. daphnia). Studies in the wild indicate that guppies are highly adaptable in their feeding habits in that guppies observed in different areas will adapt to consume a wide range of available food and, for this reason, guppies have been extremely successful when introduced into non-native areas.

Feeding should occur once daily and it is advised to alternate between flakes and live food and no more than can be consumed in two minutes or so. If there are fry in the tank then adding ground flakes and enabling them to sink in the areas where the fry gather will be beneficial to the fry.


The female guppy is attracted to the more colourful and more vigorous males, which tends to explain why male guppies, over time, have evolved to be ever-more colourful and elaborate.

The male is capable of mating from around seven-weeks of age whilst females can produce their first brood at somewhere between ten and twenty weeks of age.

The gestation period for the female is typically between 21 to 30 days, depending on temperature and other variables. In the featured image (top) you will notice the “gravid” spot just above the anal fin of the female, indicating that she is carrying young.

The female can give birth to as few as two fry and as many as 200 fry but, on average, gives birth to a range of between 30 and 60 fry.

After giving birth it is usual for the female to become gravid once more, as she will already be carrying both eggs and the sperm to fertilize them.

Well-fed adults seldom eat their own offspring but, in a general aquarium, the fry may be predated by other species so a well-planted aquarium is advised or the female can be placed in a birthing tank before being returned to the main tank after giving birth.

The guppy has been successfully mated with various species of Molly (male Guppy with female Molly) but the resulting offspring are always male and always infertile.

The Guppy has apparently evolved inbreeding avoidance. This is interesting, particularly because the female can store the sperm of multiple males over a period of up to eight months. It seems that the sperm of unrelated males are generally more successful against the sperm of related males when fertilization occurs.

Interaction with other species

Fishes with elaborate fins tend to be susceptible to having those fins nipped by other fishes, particularly when those other fishes have elongated or elaborate fins.

That said, guppies tend to rub along well with most other fish species in the aquarium and this is likely to be why they have been so successful for so long in the freshwater aquarium.

It is advised not to include any large, aggressive fish with guppies, as such fish may teat them. Some other fish such as some Tetras, Barbs and Red-Tailed Sharks as well as some Gouramis may nip the elaborate tails of the male fishes.

Many aquarists have tanks in which guppies are the only fish in the tanks due to their huge variety of colours so, bearing this in mind, you may elect to keep only guppies which, of course, will eliminate any of the few downsides of mixing them with more predatory species of fishes.

Susceptibilities of the species

Since the male fishes can have very elaborate tail fins, they can be susceptible to fungal infections so this is something that you’ll need to look out for.

As well as fungal infection, Guppies may also be susceptible to tail rot and fin rot. It’s best to ensure that you have treatments available.

Guppies can also be susceptible to White Spot (“Ick”) but this is easy to treat with one of the many off-the-shelf remedies.

Guppy standards

Guppy standards

Large strains:

  • A – Veil tail
  • B – Triangle tail
  • C – Fan tail
  • D – Flag tail

Sword strains:

  • E – Double sword
  • F – Upper sword
  • G – Lower sword
  • H – Lyre tail

Short strains:

  • I – Spade tail
  • J – Spear tail
  • K – Round tail
  • L – Pin tail

The Guppy – Videos

Featured image (top) courtesy of : Per Harald Olsen

Mike Wheeler

I started keeping freshwater tropical fish in 1972 and it has been something of a passion ever since. In this website, my aim is to build up an everyman's guide to help the everyday aquarist get the best from this inspiring and entertaining hobby.

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