Betta Fish Genetics


Use this table in conjustion with our Betta Fish Genetics Predictor to determine what will come out of your spawn!

Single/Double Tail

The single/double tail relationship is fortunately a very simple and predictable relationship. It is simply a dominance relationship – St is dominant over Dt. So StSt, StDt/DtSt are all single tail and DtDt is double tail. Simple enough eh?
Your Typical Betta, single caudal lobe

Name Abbrev Dominance Relationship Comments
Single Tail St Dominant
Double Tail Dt Recessive Double tail bettas have two distinct caudal lobes, and their dorsal fins are larger. Some Dts don’t have clean splits all the way down to the caudal peduncle, these are less desirable.


A Bettas colors are broken into four basic layers: Yellow, Red, Black, and Blue (Officially called Green) layers. The Yellow layer has no known mutations so it is unaddressed here. Unfortunately right now I don’t have any reference pictures, but i would love to get some.

Click to Enlarge
Name Abbrev Dominance Relationship Comments
Red Color
Basic Red R (Reference Point)
Extended Red Er Dominant over Basic Red All of the betta becomes red, even the labyrinth in my observation
Non-Red/Yellow Nr Recessive to Basic/Extended Red Red is Replaced by Yellow
Non-Red2/Orange Nr2 Unknown This is a farely new color, not much is yet known about it.
Red Loss Rl Dominant over Basic Red, but not Extended Red Initial red disapears partial or completely as betta matures, red may reappear, especially if the bettas fins are damaged somehow.
Normal Fins Nv (Reference Point)
Variegated Fins Vf Dominant over Normal Fins Clear or White areas appear in fins where red would otherwise be, this gene is variably expressive and is thought to be linked to the marble gene.
Black Black Bl (Reference Point)
Melano M Recessive to Black Black becomes the dominant color of the betta, overpowering almost all if not all of the other coloring. Typically Melano females are sterile, so it is impossible to true-breed Melanos, if a strain of melano was created that had consistently fertile females it would be very valuable and most likely a new mutation of the black layer.
Blond B Recessive to Black This reduces the density of the black on he body, sorta half way between Black and Cambodian
Cambodian C Recessive to Black No black is present on the body, but is present in the fins to an extent
Marble Mb Unknown Marble bettas have patches of white and black, creating a splotchly look, the pattern of which can change throughout their life.
Piebald Pb Recessive to Black No black is present in the head
Black Lace L Recessive to Black Black is present throughout the body, but it’s intensity wanes in several regions like the abodmen and caudal fin
Black Orchid O Incomplete Dominance (Note: this is CONJECTURE, I have not been able to find confirmation)
Black Orchid increases black all over the body, but doesn’t overpower the blue layer on the body and inbetween the rays near the base of the fins.
The Blue Layer is more predicable, but is also is slightly harder to understand
Green B1 Incomplete Dominance Homozygous B1B1 creates Green, Grass green is prefered over Turquoise
Steel Blue B2 Incomplete Dominance Homozygous B2B2 creates Steel Blue
Royal Blue B1B2 Incomplete Dominance Royal Blue is created by the combination of one Green allele and one Steel Blue allele – ie B1B2
Iridesence The Iridesence genes have to be the most confusing of them all, many group them in the blue layer, but Si and Op have their own pairs
Normal Iridocytes Ni (Pair 1) Recessive this is the normal iridesence gene (wild gene) it’s recessive to Si
Spread Iridocytes Si (Pair 1) Incomplete Dominance This gene makes the body look metallic, its interferes with Steel Blue, but is dominate over Normal Green, gene is variably expressive.
Non-Opaque On (Pair 2) Recessive this is the wild gene, it’s dominant over Opaque, but has no other affect
Opaque Op (Pair 2) Incomplete Dominance Iridocytes lose their luster, so the betta has no metallic sheen – a White Opaque is a Cambodian Spread Iridocyte Opaque Steel Blue Non-Red (CC SiSi B2B2 NrNr). You can have non-white opaques, this gene is also variably expressive.

Tail Shape

Less is known about tail genetics, and prediction is iffy at best. What is known is that a gene pair controls Short Fins (Sf) or Long Fins (Lf) (Plakat = sf, normal = lf), and that Long Fins is dominant. The shape genes only apply to the Long Fins bettas, and i’ve been told all Sf bettas are Vt.

Name Abbrev Dominance Relationship Comments
Veil Tail Vt Dominant Your run of the mill petstore betta, breeders don’t like this tail shape
Delta Tail X Recessive The tail is shaped like a fan, variably expressive in that the arc length of the tail varies. The abbreviation X comes from the need of a short abbrevation and other breeders using Vt/xx for this, due to the fact that delta tails arise from the complete lack of Vt genes
SuperDelta T Rcessive Between Delta and Halfmoon lays super delta
Halfmoon Hm [Multiple Inheritance] The Lovely Halfmoon tail shape, my favourite. This gene is variably expressive, most Hm * Hm spawns produce 5%-10% HMs, some very good strains get 10%-20%. The rest are delta tails but normally very close to being HM, which clearly shows multiple inheritance is involved.

Comb Trait

The (in)famous Comb trait – it seems to be an incomplete dominance relationship. With single allele being slight combing and double allele being strong combing (like that found in “Crown tails” (Super Delta + Strong Comb trait))
Once again, this is based upon my observations of the behaviors of the trait. I believe my presentation here is also a symplification, I think it may be a multiple-pair true-recessive trait (unlike halfmoon which is multi-pair and has a mix of dominant and recessive traits)
While right now I conjecture that it’s the rays that extend and not the webbing that doesn’t extend all the way, some of the fish I have seen support that it’s the webbing. If this is the case then this is independant of the trait that gives halfmoons extra webbing between rays so that they can reach 180 degree spread, because it is apparently possible to have atleast 170 degree spread Crown tails, I’ve seen them, the picture for Black Orchid above is of one that we own.

Name Abbrev Dominance Relationship Comments
Comb trait Ct Incomplete Dominance The comb trait causes rays to extend past the webbing of the betta’s fins
Normal trait Nt Incomplete Dominance The rays do not extend past the webbing of the betta’s fins