Beginner's Guide to Breeding Guppies

One of the charms of owning guppies is breeding them. With so many color and pattern variations, combined with their relatively quick reproductive cycle, there's endless possibilities to create new strains. Understanding how their reproductive system works is essential for breeders who are committed to design their own guppies. The following guides will help you understand the basics.

Determining Gender

Male guppies have pointy gonopodium at the bottom, while the females don't. Males are also smaller in size and among some strains, the tail is larger than the females. In some strains, you can easily tell the difference between males and females by just looking at the colors. 

Important Measures to Know

Female guppies are able to give birth multiple times for 6 months without the presence of any male. This means that when you buy a female guppy from a community tank/farm, there is no doubt that the female is carrying sperms from the male(s) that impregnated her. Getting a virgin female guppy is extremely hard and only dedicated breeders are willing to separate the males and females when they're still very young. If you wish to mate a particular male with a particular female, you have to understand that the female is already carrying sperm from other males that impregnated her before. Still, there is a hope that the female will give birth to from the sperm of the wanted father. It happened to mine where I just introduced my pregnant female blue grass guppy to a male yellow cobra where a month later, she gave birth and the fries turned out to be yellow cobra-blue grass hybrids which suggest that it is very possible that the sperm of the latest father can quickly become the sperm of the latest offsprings.

Another important thing to note is that male guppies are polygamous in a sense that they will impregnate every fertile-looking female. This means that the chance for a guppy colony to become inbred is very high and it is the reason why many guppies today are delicate (Inbreeding lowers immunity against parasites.). To avoid/reduce breeding, you must keep buying new guppies to introduce foreign genes. Having multiple tanks can also help. Inbreeding is one of the major problems with breeding guppies. When having multiple tanks, always label the tanks in order to keep the ancestral record.  That way, the chance of inbreeding can be reduced. Separate the males and females as quickly as possible by the time you're able to identify the gender in order to prevent incest.

How to Mate Guppies

As mentioned earlier, male guppies will try to impregnate every fertile-looking female they can find. The process of inserting sperm is so quick that it is very hard to see by our normal eyes. Males use their gonopodium to shoot sperms into the females. It is up to the females to decide whether they want to absorb the sperms or not. Furthermore, the females can also decide which sperms do they want to fertilize. Simply put a male and female together, then hope that the female will favor the sperms from the latest male. If you want to ensure for that to happen, let them live together for at least a month.

Understanding Genetics

Understanding how genetics work can help to improve your breeding results. Each guppy, like other animals with two genders, inherit one chromosome from the father and another one from the mother.

Genes can be classified into dominant genes and recessive genes. When a guppy inherits a dominant gene from one parent and a recessive gene from another parent, the dominant gene is expressed and that is why it's called "dominant" . 

Examples of dominant genes :

-Grey body (As commonly found in wild guppies.)

-Magenta body.

-Violet body.

-Snakeskin pattern.

-Varied tail colors.

-Crowntail.

-Ribbon fin.

-Zebra pattern body.

Examples of recessive genes :

-Albinism (Pale body/red eyes.).

-Scoliosis (Curved back.).

-Kyphosis (Hunchback.).

-Blond body.

-Cream body.

-White body.

-Oval tail.

Keep in mind that "dominance"of gene is actually relative to the other gene compared. For example, grey body is dominant when compared to pale body but it's recessive when compared to black body. 

As mentioned earlier, if a guppy inherits a dominant gene from one parent and a recessive gene from another one, then it's the dominant gene that is expressed. If, for example, a guppy inherits a gene to have black body from one parent and a gene to have pale body from another parent, then the appearance will look closer to the black body because black body is dominant compared to pale body. The only way a guppy can be born with pale body is if both of the genes inherited are pale. 

Let's say "B"  is dominant gene and "b" is recessive gene. If the guppy inherits the same dominant gene from both parents then the genes are "BB"  If both of the genes that are inherited are the same recessive type, then it's "bb". If the guppy inherits a dominant gene from one parent and a recessive gene from another parent, then it's "Bb".

BB = Dominant expressed

bb = Recessive expressed

Bb = Dominant expressed

If, for example, the father is BB and the mother is Bb, then the chance of the genes inherited by the offsprings are :

-BB (Dominant expressed)

-Bb (Dominant expressed)

-BB (Dominant expressed)

-Bb (Dominant expressed)

As you can see, the result will be 100% dominant expressed. 

Or we can summarize into the following formula :

BB + Bb = BB/Bb/BB/Bb

Now let us the other scenarios :

BB + BB = BB/BB/BB/BB (100% chance of dominant expressed)

bb + bb = bb/bb/bb/bb (100% chance of recessive expressed)

Bb + Bb = BB/Bb/Bb/bb (25% chance of recessive expressed or 75% chance of dominant expressed)

Bb + bb = Bb/Bb/bb/bb (50% chance of recessive expressed or 50% chance of dominant expressed)

 The following figures can help to understand how it works :

You can also apply the same formula to humans and other animals with two genders. 

As mentioned earlier, if a guppy inherits a dominant gene from one parent and a recessive gene from another parent, the appearance look closer to the dominant type. This means that if a guppy looks dominant, it doesnt mean both of the genes are dominant. In other words, if a guppy looks "B", it doesnt mean the gene is "BB". Maybe the gene is "Bb". This is why it's very important to know the genetic background of the guppy. Pure strain guppies usually have consistent background. For instance, a guppy of Black Moscow strain is guaranteed to be "BB" for the body color. On the other hand, a mutt guppy (Non-purestrain.) that looks black may not be "BB". 

Apart from understanding the difference between dominant and recessive genes, it is also quite important to understand the importance of genders. Chromosomes are divided into X-chromosome and Y-chromosome. X-chromosome is female inherited, while Y-chromosome is male inherited. Female guppies carry X-chromosomes from the mother and father (XX), while male guppies carry X-chromosome from the mother and Y-chromosome from the father (XY). By understanding this, we can see why there are features that can only be found among males that are absent among females. Those male-exclusive features are inherited by Y-chromosome and since females do not inherit Y-chromosome, they are not able to inherit the Y-chromosome features.

Examples of features that can only be found among males (Y-chromosome) :

-Large dorsal fin.

-Among some strains of guppies, the males have full body color, but overall, male guppies have more colorful body.

-Snakeskin pattern.

Since females do not inherit Y-chromosome, the only way to inherit these male-only features is to inherit it through the males. For instance, if you wish to inherit the snakeskin pattern, then it can only be inherited by your male guppies. If you do it with your female guppies in which they mate with non-snakeskin males, then the genes that give them snakeskin will be gone in the offsprings. Even though the females are siblings to your snakeskin males, they no longer carry the genes to generate snakeskin pattern.

The conclusion is that the male features that you want to have in the next generation of males must be present in the father and that the genes of the females can still affect the result of the male offsprings. 

Improving "Quality"

To improve the color quality of the fish, you might want to try some inbreeding methods. Line breeding is a method to maintain certain color/pattern/physical qualities by mating guppies with close relatives such as 2-3 generation cousins. There is also the method of backcrossing which is mating the guppies with the parent in order to achieve the appearance of the parent. Ofcourse, if you want to maintain the male features then it means it's the females that are mated with their father.

Selective Breeding

Because not all of the offsprings will look the same despite having the same parents, selecting which offsprings should reproduce is very helpful in passing down the wanted physical traits. For intance, you want to create guppies with black body and white tail by mating male black guppies with female white guppies. Through the process of selective breeding, you remove offsprings with black tail so that the next generations will have white tail. You also remove males with non-black body so that the next generation males will have black body. As the result, the latest generation males will have black body and white tail (Black body can only be inherited by males.).

Since the male features can only be inherited by males, it would be better to focus on altering the appearance of the males instead of the females. The females still play an important role in affecting the outcome of the male offsprings though. Through the process of selective breeding, we should remove males that lack the male-only features that we want and remove either males or females that lack the features that we want. To make recessive genes more prominent, mate them with foreign guppies that also carry the same recessive genes.

Additional Facts 

-Female guppies are able to decide which sperms should they fertilize into fries. 

-Female guppies are able to detect siblings and avoid incest but only if the siblings have impregnated them before.

-Female guppies have the ability to reject sperm.