While this has always been tricky, this is a task which is becoming more and more difficult as females available in Australia are becoming more vibrant in colour and better-endowed with fins, and more plakat (short-finned males) are available for purchase at a LFS.

The common identifiers between male and female bettas are listed below, but unless a betta actually lays eggs, or its eggs are actually visible inside its body, none of these is a foolproof test of whether your betta is male or female.

Experts frequently fall into error in sexing bettas, especially juveniles, so if you cannot quite work it out or you make mistakes, you are not alone.

Colour vibrancy

Once upon a time, female bettas were described using adjectives such as drab and brown. Those days are well and truly gone, thankfully, and female bettas are available which are as colourful and beautiful as the males. So if your bettas is drab and brown, odds are it is frightened, ill or unhappy, rather than probably being female.

Caudal length and ray branching

This is a far easier criteria for identifying the sex of a betta in mature long-finned bettas, rather than juveniles or adult plakats. If your fish clearly has the long flowing fins of a HM, CT, DT or VT, it is a male. Unfortunately, however, if it has shot fins it may simply be a juvenile long-finned betta, or a plakat male.

Additionally, more long-finned females exist, including some remarkable and beautiful breeder type females. These females are quite masculine looking, with multiple branching of their fin rays, especially in HM strains. They are favoured by breeders of HMs as they are more likely to result in HM offspring when paired with a HM male. Some of the best of these females have occasionally turned out to be juvenile male long-finned bettas, or male plakats.

So unless the betta is immediately recognisable as a male HM, VT, DT or CT, caudal length and ray branching are not guaranteed ways of sexing a betta.

Ventral fins

Male bettas are expected to have longer ventral fins than females. The show standard for plakats (both HM and traditional) calls for ventrals that are 1/3 the overall length of the fishes body as a minimum.

If your fish has very long ventrals, it is probably male. However, male fish do exist with short ventrals, especially those influenced by the rosetail trait.

So while the presence of short ventrals is no guarantee that your betta is a female, it is more likely that a short-tailed fish with an ovipositor (see below) and short ventrals is a girl than a fish with a short tail, ovipositor and long ventrals.

Body shape

Male bettas tend to have a narrower, more streamlined body shape. Females tend to be rounder and shorter in the body. But again this is no guarantee. It is especially difficult to sex young fish that have just eaten for this reason.

Vertical stripes

This method of sexing bettas is only applicable to darker bodied fish such as blues and coppers, not Cambodians, yellows, pastels etc. Other methods exist to sex the light bodied bettas, which are discussed below.

When darker bodied bettas are stressed, they display fear stripes, being horizontal stripes that run the length of their bodies, from head to tail. Breeding stripes, however, are quite different. Several distinct, thick vertical bars are displayed by dark bodied females who are attracted to a flaring male. This is co-incident with the fishes overall body colour darkening and becoming more vibrant, quite the opposite to fear stripes - where the bettas colour is washed out and its yellowy base colour shows under the stripes.

If your betta deepens its colour and displays vertical bars in the presence of a male, odds are it is a female.

Visible ovary

In pale bettas, such as pastels, yellows and Cambodians, if a light is shone on the body of the betta and it is female, you should be able to see the fishes ovary. This is a roughly triangular pale mass behind the dark mass that is the bettas stomach. Sometimes the ovary is so obvious that individual eggs can be seen inside the betta.

If you see eggs, congratulations! You have identified a female betta.

Flaring

Both male and female bettas flare, both at their own sex and at the opposite sex when they can see them through their container. The fact that your betta flares is therefore no guarantee that it is male.

There are some subtle differences in the manner of flaring between male and female bettas though. Male bettas often (but not always) turn sideways onto an opponent and cross their ventral fins. Female bettas often, after a while, flare at male bettas in a submissive, head-down posture. They are unlikely to do this straight away, so patience is called for if you intend to use this as a component of sexing your betta.

If your fish has an ovipositor, short fins, flares head down and displays vertical stripes, it is very likely to be a girl... probably.

Gill membrane

Under a bettas gills is a membrane, often called a beard. In male bettas this tends to be more pronounced than in females. The presence of a well-developed beard suggests that a betta is a male. But there are of course increments of development, and some male bettas have a less pronounced beard than others. So this again is not a foolproof indicator of a bettas gender.

Ovipositor

It is a common misconception that the presence of an ovipositor (the white speck between a fishes ventral fins) is evidence that it is a female. Unfortunately, life is not that simple. Numerous males display the ovipositor, so much so that in IBC shows it is a disqualifying characteristic in a male.

So, if your betta has an ovipositor, it might be a female. But if it also has long fins it is probably a male. Even if it has short fins and an ovipositor it may be a plakat male. So close, but no cigar!

Bubble nest

Another common misconception is that only males build a bubble nest. This is not true. Females build bubble nests too. In fact many have been witnessed to create a bubble nest, drop a load of eggs, place the eggs in the nest and tend to them, before they are eventually eaten!

One of my own juvenile fish, who I would have sworn due to her body shape and fin development was a plakat male, just pulled this very trick on me. But that is great as she is a gorgeous female, and one I will not hesitate to use in my breeding plans now.

Which brings us to:

Egg laying

If you betta lays eggs, it is a girl. No ifs, ands or buts! You have struck the jackpot, a guaranteed girl!

Summary

So, to summarise, these are the indicators that your betta is probably male:

- Long tail, multiple ray branching

- Long ventral fins

- Absence of an ovipositor

- Full beard

- Flares in a sideways posture with crossed ventrals.

- Narrow, streamlined body shape

These are the indicators that your betta is probably female:

- Short tail

- Shot ventral fins

- Presence of an ovipositor

- Vertical breeding bars in the presence of a male

- Flares in a head down, submissive posture (eventually)

- No pronounced beard

These factors indicate that you have a definite female:

- She lays eggs

- She has a visible ovary

Still have more questions about Sexing your Betta? Need more information? Swim on over to the forum!