My Knowledge Base - Guppy Breeding

This post documents what I have learned about breeding guppies so far:


Guppies are very very easy to breed

Apparently too easy...two of my females arrived at home already pregnant. The females (even the pregnant ones) were immediately harassed by the males as soon as they entered the tank. Needless to say this kind of takes the first generation results out of my control, since I am unwilling kill all of the first generation offspring.

Females can store sperm for future use, which gives the illusion of "virgin" births even when no males are kept in their tank. A female can use stored sperm to impregnate herself as much as six times before she runs out


Guppies are prolific and grow fast

Baby guppies are referred to as "fry".

Guppies can be impregnated as early as 3 weeks of age, so males and females need to be separated by this time to avoid accidental impregnation.

Gestation is typically around 30 days, so a newborn guppy can begin giving birth at less than two months of age. Labor is between 1 and 12 hours, though stress can cause the mother to re-absorb them in the womb or to stop giving birth altogether. Guppies can be re-impregnated immediately after giving birth.

A fully grown adult female will typically give birth to between 2 and 30 offspring but large females can give birth to 100 or more. The fry are small...between 1/2 and 1 centimeter long. The mother will birth them one at a time. The fry are born fully formed, and look like miniature versions of the adults. They swim in fast but short bursts, and will usually head for available plant cover immediately after birth to avoid the adults, which will readily eat them. This is usually insufficient to prevent losses, so a separate "nursery" tank is probably a better idea.

Guppies reach adult size at about 3 months. Adult size is between 1 and 2 inches. Females are larger than males.


Guppies are horny

Males will continually chase females and in the absence of females will chase each other. If the ratio of males to females is too high, the males could kill the females by not allowing them to rest. For this reason, guppies are typically kept only in pairs (one male and one female) or trios (one male, two females). Or the sexes are kept in entirely separate tanks.