Unveiling the Mystery: Can Guppies Really Have Babies Without Males?

Guppies, also known as millionfish or rainbowfish, are one of the most popular freshwater aquarium fish species. Aquarists love them for their vibrant colors and patterns, friendly demeanor, and ease of care. But guppies are also famous for their impressive breeding capabilities, with females capable of producing dozens, if not hundreds, of fry every month.

However, a common question that often arises among guppy keepers is whether or not guppies can reproduce without males. It is a topic that generates a lot of confusion and conflicting information on the internet. In this article, we will explore the fascinating reproductive behavior of guppies and try to understand how they are able to reproduce without males.

Female Guppies Can Self-Impregnate

It is not uncommon for female guppies to give birth without ever coming into contact with a male. This phenomenon is especially noticeable in female-only tanks, where some females continue to produce offspring despite being isolated from males for extended periods. This has led to many misconceptions and speculation about whether guppies can change sex or self-inseminate.

In reality, female guppies are capable of self-impregnating, but not with their own sperm. Instead, they store the sperm of males they have previously mated with inside their bodies for later use. Guppies belong to a group of animals called sperm hoarders, which includes the regular octopus, some fly species, the eastern diamondback rattlesnake, and even domestic chickens.

The female’s body feeds the spermatozoa with sugar, keeping it viable for longer periods of time. This behavior can lead to unexpected pregnancies, with females producing offspring even when they have not had access to males for a long time.

It is worth noting that the stored sperm can come from genetically superior males that have already died. Female guppies can preserve the sperm of a male with favorable genetic traits and use it for self-fertilization long after the male’s death. This ability allows them to maintain genetic diversity and ensure the survival of their offspring.

The Limitations of Self-Impregnation

The length of time that female guppies can store sperm varies, with the limit being approximately eight months. However, many female guppies run out of stored sperm after just three months. This difference in storage time may be influenced by environmental factors, such as the presence or absence of males in the habitat.

Despite the ability to self-impregnate, female guppies still prefer to mate with males. It is unclear why they would opt to use stored sperm rather than mating with genetically fit males around them. Researchers are still studying this behavior to gain a better understanding of its evolutionary significance.

How to Identify a Pregnant Guppy

Female guppies undergo various physical and psychological changes during pregnancy, making it relatively easy to identify when they are expecting. Physical signs of pregnancy include an inflated belly that gradually swells after the 14-day mark, a gravid spot that appears as a dark abdominal area, and hiding behavior.

Pregnant females will actively avoid males, especially pushier ones, and will retreat among plants, rocks, wood, and caves in the lower half of the tank. Additionally, pregnant females may display changes in feeding behavior, eating more and becoming more aggressive during feeding times. Refusal to eat may indicate that labor is imminent.

When labor sets in, the female will stop swimming and eating, sinking near the substrate. They will also experience shakes and convulsions as the fry are delivered, a process that can last several hours, particularly for inexperienced female guppies.

What to Do With Guppy Fry

If you plan to keep guppy fry, it is best to move them into a separate breeding tank soon after birth. This will minimize stress during delivery and eliminate the risk of fry being eaten by adults. You can also opt for selective breeding to obtain unique specimens for personal use or selling.

In this case, you will need several breeding tanks and a higher level of discipline and organization to separate different generations and track the most desirable traits.

If you don’t want to deal with guppy fry, allow them to be born in the main tank. Adult guppies will appreciate the food since they have no moral issues with cannibalism. In a community tank, all fish species will work together to turn the fry into quick meals. In this case, let nature take its course.


Guppies are fascinating fish with incredible breeding capabilities. They can reproduce without males and can store sperm for months, allowing them to preserve the genetic traits of superior males. However, despite their self-impregnation ability, female guppies still prefer to mate with males.

As an aquarist, it is important to understand the reproductive behavior of guppies, including how to identify pregnant females and care for their offspring. By providing optimal living conditions and selective breeding, you can enjoy unique specimens and help preserve the genetic diversity of these incredible fish.

Guppy Fish   Updated: March 9, 2023
avatar Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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