How To Use A Betta Fish Punnett Square? [Beginner’s Guide]

Betta fish are loved by every fish enthusiast for their colors, intelligence, and resilience. As Betta fish are known for their vivid colors and beautiful patterns, many enthusiasts have considered breeding the perfect Betta fish by themselves. Punnett Square is an essential tool to aid in that process, one which I will discuss in this article today.

A Punnett Square can help calculate the probability of a particular genotype emerging through the breeding of two Betta fish. To use implement a Punnett Square, you’ll need to know the exact genetic makeup of the parent Betta fishes. Understanding and utilizing the interaction of dominant and recessive traits will aid your attempt to breed the perfect Betta fish.

The process of breeding the Betta fish you want requires a lot of knowledge of Betta genetics, and how genotypes form. As this guide will be for a beginner, I’ll be simplifying most of the process. So, let’s explore Betta fish’s traits and how Punnett Squares work to improve your odds.

4 Key Takeaways

  • A Punnett Square is a charting system that can be used to see the probability of a desired genotype emerging from breeding Betta fish.
  • To use a Punnett Square effectively, you’ll need to know the genotypes of the parent Betta fishes.
  • The genotype with the highest probability of emergence according to the Punnett Square can also not emerge through a breeding attempt.
  • If you want to have any recessive traits emerge from your breeding attempt, you should have Betta fish who have homozygous recessive genotypes.

It’s also good to remember that the concept of the Punnett Square is based on Mendelian Inheritance, which has limitations. Other than lower probabilities emerging, Mendelian Inheritance also fails to account for instances of co-dominance and blended traits emerging. So, expect many of your breeding attempts to fail, or have unexpected results.

To ease the difficulty of understanding how to use the Punnett Square for breeding Betta fish, I’ll first touch on relevant terminology first. This will help you greatly to understand what you’re dealing with and peruse additional content for Betta fish breeding.

5 Terms You’ll Need For Using A Punnett Square

I’ll describe 5 terms you’ll encounter frequently when you explore Punnett Squares and Betta fish breeding here.

1. Genotype

The genetic makeup of any individual organism. For a Betta fish, this can be CcPPFfSs.

2. Allele

An alternate form of a gene that emerges from mutation and can be found in the same place in a chromosome. For example, blue Betta fish may have the allele C, while red Betta fish may have the allele c instead.

3. Phenotype

Phenotype is the physical expression of an organism’s genotype. For example, a Betta fish with the genotype CcPPFfSs may have a solid red color, long fins, and smooth scales. This physical expression can be called the phenotype of this genotype.

4. Dominant And Recessive Alleles

Dominant alleles will almost always cause their respective traits to emerge from a genotype, especially if they are matched with recessive alleles. Recessive alleles on the other hand are rare and typically become suppressed by dominant genes. If we consider a dominant color in Betta fish to be C, and a recessive one to be c, then we can expect a fish with Cc in its genotype to be of the dominant color.

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5. Heterozygous And Homozygous Genotypes

If a genotype contains a combination of dominant and recessive alleles, they are heterozygous genotype. However, homozygous genotypes are solely made of either dominant or recessive alleles. For example, CcPpFfSs would be an example of a heterozygous genotype while CCPPFFSS would be a dominant homozygous one.

Mind you, what letter we use to characterize an allele can be arbitrary, but capitalized letters are reserved for expressing dominant traits only.

Now that we’ve gone through the relevant terminology, let’s explore the dominant and recessive traits that can be found in the major features of the Betta fish.

Notable Dominant And Recessive Traits In Betta Fish

In our attempt to use Punnett Squares, we’ll need to account for the dominant and recessive traits of Betta fish. We’ll have to take into account how they interact as well, and then use it in our favor. I’ll list off the most notable or desired dominant and recessive traits here, listing them within the subcategories of color, fin size, and fin and tail shape. I’ll also denote the letters I’ll be using for each subcategory later for my Punnett Squares.

1. Color

For Betta fish, the notable dominant colors are the following.

  • Red.
  • Opaque.
  • Turquoise.
  • Steel Blue.
  • Royal Blue.

For my Punnett Squares, I’ll be denoting dominant color alleles with C.

On the other hand, the notable recessive colors for Betta fish are these.

  • Black.
  • Yellow.
  • Orange.

I’ll be denoting recessive color alleles with c.

Color in Betta Fish actually gets far more complicated and confusing than this. According to H.M. Wallbrunn’s Four Layers Theory, Betta fish’s color comes from 4 successive layers. I’m listing the layers from innermost to outermost below.

  • Yellow: It is the deepest layer, and it does not have any known mutation genes. Xanthophores control this layer.
  • Red: This layer is controlled by erythrophores, and it can have variations such as extended red, red loss, and variegated, or non-red genes. The extended red gene causes the red color to cover the entire body. The red loss gene will cause the fish to lose red color with age. And the variegated gene will give a spreading pattern of red, while the non-red gene will lead to yellow or orange Betta fish.
  • Black: This layer is controlled by melanophores, and it can contain the Cambodian, Melano, and blonde genes. The Cambodian gene removes black color pigments from the Betta fish. The Melano gene causes the blackness to deepen while the blonde gene lightens it.
  • Iridocyte: This outermost layer is controlled by guanophores, and it can have blue/green, spread iridocyte, and non-blue genes. The blue/green gene causes Betta fish to be of steel blue, royal blue, or green iridescent color. The spread iridocyte gene gives Betta fish a metallic shine. And the non-blue gene removes the Betta fish’s blue layer.
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The scales on top can also be metallic, “dragon”, or opaque in color, covering up the color layers underneath. What color you finally see is the combination of these layers or the most dominant color emerging from this.

This is why some color variations are much harder to achieve and complicated to even plan for. For example, a true black Betta fish would require a combination of the non-blue gene, and the Melano gene to emerge as well as the scales to be opaque. As a beginner, you’ll need to be aware of this mechanism, but it’s fine if you don’t want to dive any deep right away.

2. Fin Size

Most artificially bred Betta fish variants available on the market nowadays have long fins, as it is the most desirable trait. The allele for large fins is dominant, and I’ll be denoting this with F.

However, if you want stockier, smaller fins, you’ll find those only on the original Plakat or Siamese Fighter fish variant of the Betta fish. This is caused by a recessive allele, which I’ll be marking with an f.

3. Fin And Tail Shape

The most notable dominant fin and tail shapes in Betta fish are listed here.

  • Veil Tail.
  • Crown Tail.

For my Punnett Squares, I’ll be denoting the alleles for these traits with a T.

And these are the most desired recessive traits.

  • Halfmoon.
  • Double Tail.
  • Delta Tail.
  • Comb Tail.

I’ll denote these with a t.

Wild Betta fish have a rounded fin and tail shape, which is a trait that is suppressed by dominant genes. However, when pitted against recessive genes, it dominated them instead. I’ll not be using this type in my examples, as a beginner should use artificially bred Betta fish to start with.

Now that we’ve denoted the notable dominant and recessive trait types, let’s finally move on to using Punnett Squares.

Tracking Desired Genotype Percentage Using Punnett Squares

Let’s consider an example. We are breeding a red male Betta fish with a heterozygous dominant genotype of Cc with a female black Betta fish that has a homozygous recessive genotype of cc. We want to know what the outcome of such a breeding attempt would be.

Now let’s draw a Punnett Square with this information. We’ll draw a 4×4 table and jot down the male’s alleles on the left, and then put the female’s alleles on top. Afterward, we’ll match the male’s allele next to each box with the female’s allele on top of it.

As you can see, such as attempt would result in 2 cases of the Cc genotype and 2 cases of the cc genotype emerging. With 4 boxes total, each box here represents a possibility of 25% occurrence. That means, there’s a 50% chance that you’ll have Betta fish with a Cc genotype, and 50% that they’ll have the cc genotype.

As dominant alleles will almost always suppress recessive alleles, the Betta fish with Cc genotype will express the corresponding phenotype. In this case, they will be red. The cc genotype will retain the female’s black color.

Let’s move on to a more practical example. We’ll try to breed two Royal Blue, long-finned, and Veil tail Betta fishes with a heterozygous genotype of CcFfTt. We are aware that the recessive alleles present in their genotype are for black color, shorter fins, and a halfmoon fin and tail shape.

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The possible combinations for these alleles would be the following 8 arrangements.

  • CFT.
  • CfT.
  • CFt.
  • Cft.
  • cFT.
  • cfT.
  • cFt.
  • cft.

If we set up a Punnett Square with these combinations, we find the following.

The Punnett Square probably looks quite dizzying at this state, and very hard to parse. To make it easier on us, we need to start color-coding by dominance.

Let’s color-code the Punnett Square according to these rules.

  • Fully dominant genotypes will be highlighted in black.
  • Only recessive color allele genotypes will be highlighted in purple.
  • Only recessive fin-size allele genotypes will be highlighted in yellow.
  • Only recessive fin and tail shape allele genotypes will be highlighted in red.
  • Only dominant in color allele genotypes will be highlighted in gold.
  • Only dominant in fin size allele genotypes will be highlighted in green.
  • Only dominant in fin and tail shape allele genotypes will be highlighted in blue.
  • Fully recessive genotypes will be highlighted in grey.

The color-coded Punnett Square gives us a ratio of 27:9:9:9:3:3:3:1. As you can see, we have 27 cases where the dominant alleles will display their physical attributes in the phenotype, and only one case where a Betta fish with a fully recessive genotype would be born. There’s a high 33.33% chance of a royal blue, long-finned, and veil tailed Betta fish being born, whereas a short-finned, black halfmoon Betta would have a measly 1.24% chance of being born.

As you can see, the Punnett Square enables you to see what genotypes would be ideal to breed to create a higher possibility for your desired phenotype to emerge. You can plan by generation to increase the odds of the sought phenotype, such as breeding fully recessive genotypes with desired phenotypes to eventually breed a rare genotype.

Limits Of Punnett Squares

The Punnett Square is helpful, but it follows the concepts of Mendelian Inheritance. I’ve mentioned this throughout the article, but its reliance on Mendel’s laws makes it a faulty predictor. It does not account for co-dominance, blending, or the behavior of the alleles of a wild Betta fish.

Punnett Squares can’t predict the outcome of a single breeding either. The unique circumstances occurring in each breeding attempt are full of other variables which it was not designed to account for. It can only predict the broad pattern of mass repeated breeding attempts. So, keep this in mind during your attempts at Betta fish breeding.


Thanks to the efforts of Betta fish enthusiasts and breeders, many variants of the Betta fish have emerged over the years. Recessive alleles such as the halfmoon fin shapes are not rare and can be easily found on the market.

Whether you want a combination of recessive or dominant traits, you can find your desired parent Betta fish easily. And if you want to dive even deeper, you can explore forums and blogs to learn from other enthusiasts’ and breeders’ experiences with Betta fish breeding.

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Muntaseer Rahman

About Author

Hello, I’m Muntaseer Rahman, the owner of I’m passionate about aquarium pets like shrimps, snails, crabs, and crayfish. I’ve created this website to share my expertise and help you provide better care for these amazing pets.


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