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Blue betta fish: characteristics and genetics

Updated: Dec 30, 2023

Did you know that there are different shades of colors and types of bettas? That is, blue bettas, in particular, are different from each other. Red bettas in the same way. That is, if you look closely, you will see that each betta is a betta, even if they are from the same litter.

What you will learn

In this article we will deal with the characteristics of the shades of blue in bettas, specifically. When you finish reading, you will know a little more about the Bl and bl genes, responsible for the blue color. Also, you will be aware of the visual characteristics of bettas of this basic color.

We will not discuss the origin of the betta we have in our aquariums in this article, commonly available in pet shops and breeders. However, be aware that the blue betta is a viable and fertile hybrid.

Blue betta traits

The Bl and bl genes are responsible for part of defining the blue color type in bettas. According to the principles of applied genetics through Punnett Squares, there are three possible combinations of these genes, as follows:

  • Bl Bl

  • Bl bl

  • bl bl

Each of these imparts a basic color on the betta's body. Note, however, that there are four theoretical layers that produce color in bettas, each compounding the other as the case may be.

We are dealing here with the Iridescent Colors Layer. This layer overlaps the other layers when active, and these two genes, in the three phenotypes above, initially composed the genetic modeling of this color. Crosses between different species of bettas resulted in a greater amount of genes defining the colors, color arrangement and shapes of the bettas.

In this way, current bettas have acquired an additional pair of alleles to define the final color of shine that will be displayed in the betta's phenotype: the metallic, and non-metallic, traits. As a result, the three types of shine that bettas could once exhibit have now become nine different possible iridescent colors.

We, at the Betta Project, represent the presence of the metallic trait by the * gene, and for the iridescent bettas without the metallic trait (which are the ancient iridescent bettas, or also called traditional, respectively, the Royal, Turquoise, and Steel blues ), we used the nm gene (acronym originating from the initials of the words “non-metallic”) as symbology.

So, there are three possible combinations of these two genes:

  • **

  • * nml

  • nm nm

Below we show the genetic modeling for all possible iridescent colors involving these two pairs of alleles in bettas:

Metallic bettas

Intense green

Teal Blue


Traditional or non-metallic bettas


Royal blue

Steel Blue


We deal here with the genetic modeling of iridescent colors (also called structural colors, involving the Bl/bl and */nm genes.

Added to these two pairs of genes (Bl/bl and */nm) that always work together, we also have the tonality of this iridescence (if darker, if lighter, if more lit, if more dull).

Were you interested in knowing more about Betta Genetics?

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We wish you success with your bettas!


[1] Betta Project internal archive.

[2] Images from Internet.

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