Guppies for Aquariums 

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.

Taxonomy 

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.

Distribution 

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.

Species 

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, & Isbrücker, 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".

 Guppies: Poecilia reticulata

Half Black Blue Delta male	Albino Gold female	Platinum Sunset male

Golden Snakeskin male	Red Delta male	Sunset Blue Metallic male
Multicolor Mosaic Delta male

Besides colours, breeders have created guppies with modified dorsal and tail fins. Veil-tail forms are especially common. These guppies have long flowing dorsal fins and tail fins that are two or three times larger than those of wild guppies. One problem with these veil-tail forms is that they are simply not as good at swimming as guppies with normal-sized fins. This causes problems for them in tanks with strong water currents and also at feeding time, when they find it difficult to compete with regular guppies. Veil-tail fish are often targeted by nippy tankmates such as tiger barbs and Serpae tetras, and even species not usually considered fin-nippers, such as angelfish and Synodontis nigriventris, have been known to nibble on these slow-moving guppies. As well as veil-tail forms, there are guppies with single or double sword-tails, pin-tail guppies, and round-tail guppies. The popular delta-tail guppy has a large tail that is similar to the veil-tail in size but instead of being rounded is a neat triangular shape. 

Ender guppy varieties 

Wild Endler guppies are found in a number of different forms. The variety found in the Campoma lagoon and its immediate surroundings is the standard form. Males are silvery-white with red-orange markings and a prominent comma-shaped black mark on the flank about halfway along the body. The form from the Carupano region lacks this comma-shaped marking. 

Artificial varieties have different colour patterns, and in many cases these have been bred into the Endler guppy by crossing it with common guppies. Often the males of these hybrid guppies are noticeably larger than wild Endler guppies. Also typical of these hybrids are colours not seen on pure-bred Endler's, such as snakeskin patterned tails. 

Water chemistry 

The common and Endler guppy are both naturally found in hard, alkaline freshwater environments. They do not do well in soft and acidic water, but beyond that they are supremely adaptable. The typical municipal water around pH 7.5 and 20 degrees GH is just about perfect for guppies of both kinds. They can be also kept in brackish water, and make a good addition to the low salinity brackish water aquarium containing species such as gobies or killifish. 

The swamp guppy is more particular about its living conditions, and seems to need slightly brackish (at least SG 1.003) to do well. When making brackish water, always use proper marine salt mix, not "tonic salt". 

Basic care 

In terms of general care, all the guppies are very similar. They enjoy a mix of planted and open areas, and floating plants in particular are valued by the fry as a good hiding place away from potential predators. Provided they water chemistry is within their range of tolerances, guppies make excellent additions to the planted aquarium and cause no damage at all. Being relatively small fishes, they can be easily maintained in even quite small aquaria. Having said that, a 10 gallon tank should be seen as the minimum for a small group of guppies. 

Water quality is important, and in polluted aquarium or immature aquaria fancy guppies especially become prone to a variety of complaints including Finrot and fungus. While they are often suggested as ideal fish for maturing new aquaria, this isn't a good idea if the only guppies you have access to are fancy guppies. Wild guppies and "feeder" guppies are considerably tougher, and can, with care, be used to cycle aquaria, though as ever it is important to monitor water conditions during this phase and perform regular and substantial water changes as required. 

Guppies are generally inoffensive towards their tankmates, though males will spar with one another and often harass unresponsive females. It is quite common to keep males by themselves, but obviously doing this won't lead to baby guppies! A ratio of 2-3 females to every male seems to work well if you want to maintain a breeding population of guppies in the aquarium. Like any other small fish, guppies are easily bullied or eaten by substantially larger fish. Male guppies are small enough to be eaten by otherwise "harmless" community fish including angelfish and Pimelodus pictus. Fancy guppies are also very vulnerable to being fin-nipped, so should not be kept with any fishes liable to do this (Serpae tetras, black widow tetras, tiger barbs, etc.).

Diet 

Guppies are omnivores with a preference for insect larvae such as mosquitoes and bloodworms and small aquatic crustaceans such as daphnia and brine shrimp. They also appreciate some greens in their diet. This can be provided partly by allowing them to nibble on algae in the aquarium, but it is also a good idea to use a Spirulina-based flake food instead of the regular kind. Often, this vegetarian flake food is sold as "livebearer food" and it works equally well with guppies, mollies, and platies. 

Breeding 

Breeding guppies is straightforward. As with other Poeciliid livebearers, the males fertilise the females using their modified anal fins. Gestation lasts about three to four weeks, and broods typically contain about twenty fry, though much larger batches have been reported. Female guppies can be cannibalistic, so many aquarists prefer to confine pregnant females close to giving birth to "breeding traps" that separate the mother from any fry she produces. While this works, it does tend to stress the female, and a good alternative is simply to put lots of floating plants, such as hornwort, in the aquarium. The newborn fry instinctively hide in the plants where they can be easily removed to a rearing tank. 

Guppy fry are easy to rear on powdered flake food and algae. Four to six small meals a day seems to work best, though this does mean that water quality should be monitored carefully, and regular water changes are important. Under good conditions, the fry grow rapidly and mortality rates are very low. Sexual maturity can be reached after as little as 2-3 months, though more commonly the females do not start producing batches of fry until they are around 6 months in age. 

Part of the attraction of keeping guppies for advanced fishkeepers is creating their own varieties. This is practically a hobby in itself, and several excellent books cover the subject in great depth (see the reference list below). It is also well worth spending time talking with guppy breeders to learn from their experiences. Many countries have livebearer or guppy clubs, and these regularly hold auctions and shows where neophyte guppy breeders can spend time with more experienced breeders as well as obtain good quality breeding stock.

Diseases 

Guppies can suffer from all the usual complaints that aquarium fish may be troubled by, such as Whitespot, and when kept in soft and acidic water conditions slime disease, Finrot, and fungus are especially problematic. They also become liable to sickness when kept in water that is too cool. One disease peculiar to guppies is "guppy disease", caused by the protozoan parasite Tetrahymena. This is a Whitespot-like disease though with a few additional symptoms, typically obvious damage to the skin, protruding scales, and odd swimming behaviour. Treatment for light cases is the same as for Whitespot, though you may need to perform the treatment several times to wipe out severe cases.

The not-so-humble guppy 

While not quite as indestructible as popular belief would suggest, guppies remain good fish for aquarists with limited experience but anxious for something lively, colourful, and easy to breed. Endler guppies and swamp guppies add a touch of exoticism to this aspect of the hobby, having all the positive attributes of their "common" cousins while differing just enough in terms of colouration to make them distinctive and desirable. Whichever guppies you go for, they are all fun fish with lots of personality and few shortcomings. All in all, excellent aquarium fish.

References 

Scott, P: Livebearing Fishes (Fishkeeper's Guides), Interpet Publishing, 1999, ISBN 1-9023-8962-X

Dawes, J: Livebearing Fishes: A Guide To Their Aquarium Care, Biology and Classification, Blandford, 1995, ISBN 0-7137-2592-3

Iwasaki N: Guppies, Fancy Strains and How to Produce Them, TFH 1989, ISBN 0-8662-2702-4

Monks N. (editor): Brackish Water Fishes, TFH 2006, ISBN 0-7938-0564-3

Schafer F & M. Kemkes: All Livebearers and Halfbeaks, Aqualog 1998, ISBN 3-9317-0277-4

Schroder J: Genetics for Aquarists, TFH 1976, ISBN 0-8766-6461-3

Shubel S: The Proper Care of Guppies, TFH 1995, ISBN 0-8662-2615-X