Guppies are among the most popular livebearers thanks to a combination of small size, bright colours, peaceful behaviour, adaptability, and hardiness. They are often recommended as ideal beginner’s fish, and to some extent that is justified, as few tropical freshwater fish are as easy to maintain or breed as guppies. But their tolerance for poor water conditions and slack aquarium management can be easily overestimated, and fancy guppies in particular are not nearly as hardy robust as their wild ancestors. On the other hand, in a properly maintained aquarium with suitable water conditions guppies are largely problem-free animals, and the ease with which they can be bred has made them attractive to generations of aquarists as well as educators and scientists.
Common Name: Guppy
Scientific Name: Poecilia reticulata
Origin: Americas, Florida to Brazil
Size: Up to 1 ½” (3cm) for males, up to 2″ (5cm) for females
Tank Size (Minimum): 5 gallons (19L)
Difficulty Rating: Beginner
Breeding Difficulty: Easy
Temperature: 65-80°F (18-27°C)
Life span: 2-5 years
Water pH: 7.0 – 8.0
Water Hardness: Medium hard to very hard (10-30 dH)
Male and female Guppy Anatomy
Guppies belong to the family Poeciliidae, a group divided into three subfamilies, the Poeciliinae, Fluviophylacine, and Aplocheilichthyinae. The Fluviophylacine and Aplocheilichthyinae are African egg-laying killifish while the Poeciliinae are North and South American livebearers. While this combination of egg-laying and livebearing fish in one family seems a bit odd at first glance, it is worth reminding ourselves that giving birth to live young has developed multiple times in bony fishes and is not a unique characteristic of the fish aquarists call “the livebearers”. Besides the guppies and their relatives in the Poeciliinae, livebearing bony fishes may be found among the halfbeaks, surf perches, and scorpionfishes, among others. In addition, if you put aside the fact they are livebearers, guppies are really very like killifish in basic shape and ecology, sharing things like an upturned mouth for snapping up mosquito larvae, clear differences in colouration between the males and females, and relatively short lifespan but rapid rate of reproduction.
Within the Poeciliinae, the guppies span three species in two genera. The common guppy is Poecilia reticulata, a member of the same genus as the species we call mollies, such as Poecilia sphenops. Apart from mollies being generally much bigger and more stocky than guppies, the physical differences between guppies and mollies are slight. The males of some molly species have large sail-like fins of course, but otherwise the key difference is in the shape of the mouth. Mollies are equipped with specialised jaws and teeth that allow them to scrape algae more effectively from hard surfaces such as rocks. Guppies lack these modifications, and while they certainly will nibble on algae, their feed primarily on insects, particularly insect larvae. Some taxonomists have placed guppies in their own genus, Lebistes, and it is not uncommon to see this name retained as a subgenus within Poecilia, so that guppies are Poecilia (Lebsites) reticulata whereas mollies are, for example, Poecilia (Poecilia) sphenops. More recently, taxonomists have been placing the common and Endler guppies in the subgenus Poecilia (Acanthophacelus) instead.
The other guppies in the trade are Poecilia wingei, known to hobbyists as the Endler guppy, and Micropoecilia picta, the swamp guppy. The Endler guppy is extremely closely related to the common guppy and the two species will hybridise readily. For that reason, they should not be kept together. The swamp guppy is an uncommonly seen brackish water species of small size and brilliant colouration.
The origin of the common name “guppy” is interesting. An English naturalist Robert Guppy discovered the species in Trinidad while living there in 1866, and it was later described as Girardinus guppii in his honour by Albert Gunther at the Natural History Museum in London. However, unknown to Gunther the German naturalist and explorer Wilhelm Peters had found and described this fish as Poecilia reticulata from material collected in South America a few years earlier. So while Poecilia reticulata remains the correct Latin name for this fish, its common name still recalls that of Robert Guppy.
All three of the species called guppies come from the northeastern corner of South America. The common guppy originally hailed from Brazil, Guyana, and Venezuela on the mainland and a number of islands off the Venezuelan coast including Antigua, Barbados, Trinidad, and Tobago. It has now been widely distributed around the world and is established on all continents save Antarctica, generally in tropical or subtropical environments but occasionally also found in the temperate zone where it can survive in waters heated artificially, for example by waste water from power stations. Mostly guppies have been introduced to these places to combat malaria, the theory being that since they eat mosquito larvae and breed so quickly, they could help to reduce the rate at which the mosquitos transmit malaria. In reality, any effect they have on malaria turned out to be negligible, whereas the effect they had on native fishes was often very serious, competing with them for food and space.
The Endler guppy has a much more restricted distribution, and is only known from the Campoma region of Venezuela. Swamp guppies are a bit more widely distributed, and can be found in Brazil, Guyana, and Trinidad, though they are usually confined to brackish water habitats.
Poecilia reticulata Peters 1860, the common guppy. South America (Brazil, Guyana, and Venezuela) and nearby islands. Maximum size around 2.5″, males usually about half that size but with brighter colours, particularly on the tail. A very variable species, wild-caught fish are sometimes traded but mostly aquarists will find the more brightly coloured fancy guppies on sale. Does well in freshwater or brackish conditions, pH 7-8, dH 9-19, temperature 18-28 C. Wild-caught guppies and non-fancy “feeder” guppies are notably more robust than fancy guppies. Fancy guppies require a mature aquarium with good water quality to do well.
Poecilia wingei Poeser, Kempkes, & IsbrÃ¼cker, 2005, the Endler Guppy to the aquarium trade but Campoma guppy to science. Endemic to Venezuela, but only in Campoma region where the common guppy is not naturally found. Males smaller than male common guppies but more brightly coloured. Females similar in size and colouration to common guppies. In general terms maintenance is identical to that of the common guppy, except that warm water conditions are preferred, ideally around 26-28 C. Common and Endler guppies hybridize readily, and most of the Endler guppies available in pet stores are in fact hybrids of the two species. While perfectly nice fish in themselves, aquarists after pure-bred Endler guppies will do better by obtaining them from aquarium clubs, auctions, etc.
Micropoecilia picta (Regan 1913), is known as the Swamp Guppy in the trade and is referred to as Poecilia picta in many older aquarium books. It is a small species getting to about an inch or so in length and rather resembles a wild-type guppy at first glance. It is a bit more streamlined than the average guppy though, and its tail is not so large. Coloration is very variable, and a number of aquarium strains have been developed. Typically the fish is silvery-green with patches of yellow, blue, and black. Males are smaller but more colorful than the females. A brackish water species, the swamp guppy does not do well kept in a freshwater tank; pH 7.5-8.0, hardness 20 dH or more, specific gravity 1.003-1.005. Temperature 26-28 C.
Fancy guppy varieties
Describing the full range of fancy guppies available is impossible. Fancy guppies can be found in practically every colour imaginable, some entirely one colour, others a mix of colours. Blue and red guppies are particularly popular. There are of course albino guppies as well as all-yellow “blonde” guppies. Guppies with snakeskin patterns on their bodies and fins are very popular, and any number of varieties have been produced, such as “king cobras” and “green snakeskins”.