Breeding Guppy

How to breed Poecilia reticulata: livebearer biology, gonopodium and sexing, gestation, brood size, sperm storage, and protecting newborn fry.

Overview

The Guppy (Poecilia reticulata) is a prolific livebearer rated beginner-level for breeding. Females give birth to free-swimming fry rather than laying eggs, and reproduction often occurs spontaneously when both sexes are present.

Sexing

Males are typically 1.5-4 cm long, while females are larger at 3-7 cm. The male's anal fin is modified into a tubular gonopodium with a channel through which sperm bundles are transferred to the female; females retain a fan-shaped anal fin and are plainer.

Conditioning the Breeders

Guppies are polyandrous, with females mating with multiple males, and males provide no parental care. Females can store sperm in the ovaries and gonoducts and continue to fertilise ova for up to eight months. Males mature in 7 weeks or less, and females first produce offspring at 10-20 weeks of age.

Spawning Behavior & Birth

Gestation ranges from 20 to 60 days at 25-27.8 °C, depending on several environmental factors. A female drops two to 200 fry at a time, though the figure typically ranges between 30 and 60, with birth occurring over a period of one to six hours. Because males benefit from frequent mating and provide no parental care, a single female may be pursued by several males.

Fry Care

Well-fed adults rarely consume their own young, but safe zones are still required. Well-planted tanks that offer barriers to adult guppies shelter the young quite well, with guppy grass, water sprite and java moss being effective. Specially designed livebearer birthing tanks suspended inside the aquarium can also protect the female from harassment during birth and shield newborns from being eaten.

Common Challenges

Predation of fry by adults is the main loss, so dense cover or separation is important. Sperm storage in the ovaries and gonoducts, lasting up to eight months, means a single mating can produce successive broods even after the male is gone, which can lead to rapid and unplanned population growth in a community tank.