To a new keeper, telling male and female betta apart can be quite difficult. They seem to look nearly identical, especially when it comes to short finned varieties such as Plakats. Their colors can be the same, their body shapes are very similar, and some types have similar fins. So how do you tell them apart?
The best way to differentiate male and female betta fish is by using multiple methods, instead of relying on just one. That being said, using the fins is often the easiest and most reliable. You can also determine sex by looking at other secondary sex characteristics, such as the egg tube females have, but males can have a faux egg tube.
In this article, we will discuss fins, beard, keeping them together, coloration and exceptions, size, ovipositor and exceptions, and requirements for the sexes.
In the most simple of terms, male betta fish have longer fins than female betta fish. The fins of a female also tend to stay closer to the body, while the fins of some males flare out away from the body. This is normally seen with the tail, anal, and dorsal fins.
Looking at the ventral fins is often the easiest way to differentiate male from female. The ventral fins are the two little fins that hang down from the body and are almost underneath the gills. These fins look like thin sticks, as there is not much to them.
A male’s ventral fins will be significantly longer than that of a female’s, no matter what species or type. If you are looking purely at fin length and happen to have a Plakat male (a short finned variety) and a long finned female, some of the female’s fins may be larger than the male’s, but the ventrals will not.
That being said, it is not uncommon to see bettas with damaged or missing ventrals, especially with new breeders. Certain types of food, namely microworms, will burn off part of the ventral fins if overfed. In this case, you may find a male with very, very small ventrals.
A beard? On a fish? That’s right, just like humans, male betta fish have beards and female betta fish do not. Unlike humans, these beards are significantly different.
The beard is a membrane that is hidden behind the gill plates, or the gill coverings. On a male betta, this black membrane will not entirely fit behind the gill plates and will stick out around the edges.
Some female bettas also have beards, but they are not visible when the gill plates are down. If the female flares and forces her gill plates to the sides, a beard can sometimes be seen, but it is not as impressive as a male’s beard.
The purpose of the beard is to make the betta look bigger when it flares. The whole display of flaring out the fins, gill plates, and beard, makes the betta look bigger and more impressive. This display is seen during both spawning and instances of serious aggression.
“Keeping Them Together”
One common piece of advice is to “put them together. If they fight, they are both males”. This is incredibly wrong on many levels. The first issue is that this is a flat out lie; if you put two females together, one will kill the other.
If you put a female and a male together, they are not going to get along. The male may not kill the female outright, but he will after a few hours to a few days, and the female may kill the male. While most females are less aggressive than males, this is by no far a quantifiable measure. Many females are aggressive, many males are aggressive, and females will kill other bettas, just like the males.
The second issue with this “advice” is that it is entirely unethical. Throwing any two bettas together, even a pair that has previously spawned, will result in severe, and often lethal, damage. While it is possible to condition a male and female pair, the damage will still be severe, all you have to do is google a before and after. The pictures are terrifying.
This method is entirely inaccurate and cruel. If you put two bettas together, no matter the gender, the most aggressive and strongest will kill the weaker one. There is no guarantee that the weaker one will be a female. I’ve had my female severely injure my male during spawning.
Coloration and Exceptions
In general, female bettas have duller and lighter colors than male bettas. The males will have a more vibrant and rich color overall. Of course, many factors contribute to this, mainly diet, tank size, temperature, and water parameters.
Since a sick betta will also display muted colors, you must first ensure that the fish is not sick. Check all your parameters, then observe the fish carefully for signs of disease. If your ammonia and nitrite are at 0 ppm, your nitrates are at or below 20 ppm, you see no other signs of illness (such as lethargy, gray or white patches, refusal or food), and your temperature is between 78-82, you can rule out sickness.
Female bettas are still quite beautiful and can be vibrant, especially the blue and red varieties, but they will be less vibrant than their male counterparts. Of course, there are always exceptions.
The main exceptions are koi plakat bettas, as the females can be just as vibrant as the males and have similar fin lengths. They can be different to differentiate, and the best way to differentiate the sexes is the fin length.
Cellophane bettas can also look similar, as they are light colored bettas with occasionally clear fins. While it is difficult to differentiate based on color, most cellophane bettas are of the long-finned varieties, so it is easy to tell the sexes apart.
Male bettas end up growing a bit larger than the female bettas, sometimes by as much as an inch. The size difference is most easily observed in the long-finned varieties, as the long fins plus body length could make the males two or more inches larger than the females.
Even though females are the ones who carry 100-300 eggs, the males are longer, while the females tend to be thicker, especially if they are carrying eggs. The males need to be larger and have larger fins so that they look bigger when flaring.
They flare both to look bigger and to defend their nest from predators. Their larger size is primarily to increase the chances of survival of the eggs and young, as the males provide parental care for them while the females do not.
There are other factors that come into play here, including water parameters, temperature, growth inhibiting hormones, and food. Poor water parameters, incorrect temperatures, and a lack of food will result in a smaller betta.
Young bettas release a growth inhibiting hormone, which is not usually an issue, but if their water is not changed enough, they will stunt themselves. I have personally seen an adult male betta that has a body length of ¾” due to this phenomenon but has fully formed fins.
Ovipositor and Exceptions
An ovipositor is also called an “egg-spot” and is the white raised dot protruding underneath a female’s bettas belly, right behind the ventral fins. Most of the time, this is a very accurate way to sex bettas, as males do not have eggs.
That being said, young bettas, and some old bettas, will have false egg-spots. I had one male that showed a false egg-spot and was still able to breed. He showed the false egg-spot for his entire life but was otherwise obviously a male.
Requirements for the Sexes
While some of the impaired long-finned bettas can live in a 2.5 gallon, most of them cannot, and females definitely cannot. The very long finned bettas are unable to swim properly, and as a result, do not need as much swimming space.
For shorter finned male bettas and female bettas, they need a tank of at least five gallons in order to live a happy life. In addition, it is much easier to do water changes on a 5 gallon and keep the water parameters (ammonia, nitrite, nitrate, and temperature) in check.
Female bettas can also become egg bound, which is a medical issue in which she produces too many eggs and it causes severe bloating. Showing her a mirror or a picture of the male betta can sometimes cause her to release the eggs but fasting is normally the best way to fix this issue.
In conclusion, male and female bettas can be differentiated by fin length, beards, size, coloration, and ovipositors. However, there are normally exceptions to these rules, as all of these factors are decided by more than just sex. By using all of the factors, you should be able to easily determine the sex of your fish.