Guppy

About the species

The guppy (Poecilia reticulata) is a small livebearing fish from South America that gives birth to fully formed live young rather than laying eggs – one of the traits that most clearly sets it apart from shoaling species like the neon tetra or predatory cichlids like the angelfish. Thanks to its tolerance for a wide range of water hardness and its easy breeding, the guppy is widely recommended among aquarists as a beginner species, It is named after the naturalist Robert John Lechmere Guppy, who sent specimens to the Natural History Museum in London in the mid-19th century, and a female carries her young for a relatively short gestation, typically around four weeks.though keeping one well still requires basic knowledge of sex ratios and group size.

Aquarium and equipment

A small group (for example one male with two to three females) can be kept in roughly 40 litres, though as with most shoaling fish a larger volume is always the safer choice, since it buffers fluctuations in water quality. Guppies are active swimmers in the middle and upper water column, so dense planting gives fry and shyer females places to hide.

Water: temperature, pH and hardness

The guppy is a tropical fish and needs heated water, typically between 22 and 28°C. Unlike many South American species from soft, acidic water, guppies originate from areas with hard, alkaline water and do best at a pH between 7.0 and 8.5 with relatively high general hardness. Recommended carbonate hardness (KH) is roughly 5–15 °dH, which helps keep pH stable. Water that is too soft or too acidic weakens their resistance over the long term, so they are not a good match for species that need soft, acidic water in the same tank.

Breeding and population control

The guppy is a livebearer – the female gives birth to fully developed young, typically every four to six weeks if a male is present. Without a planned sex ratio (more females than males is recommended), the population can quickly outgrow the tank's capacity, and fry are often eaten by adult fish if the tank lacks enough hiding places. Anyone who does not want breeding should consider a females-only or males-only tank.

Tankmates

Guppies are considered a peaceful species and get along well with other livebearers, rasboras and corydoras catfish, but fin-nipping species should be avoided since they can damage the males' long, colourful fins. Angelfish and other larger, predatory species may treat adult guppies, and especially fry, as food.

Diet

In the wild guppies feed mainly on insects, larvae and small invertebrates; in the aquarium they readily accept good-quality flake or pellet food, supplemented with live or frozen food such as brine shrimp. A varied diet improves colour and vitality, while overfeeding quickly loads down water quality in smaller tanks.

Colour varieties and what to look for when buying

Decades of selective breeding have turned a relatively plain wild form into hundreds of colour and fin varieties, from large fan-shaped tails to short, compact forms. When buying, it is worth choosing lively, active individuals without clamped fins or cloudy eyes, since some heavily inbred, mass-produced lines are less hardy than plainer, less ornamental strains.

Who the guppy suits

The guppy is among the most commonly recommended fish for beginners thanks to its quick adaptation to a wide range of water parameters and relatively low equipment requirements. Anyone choosing one should still think ahead about sex ratio and potential offspring, since a smaller tank can otherwise become overstocked quickly.

Pros & cons