The question of how long are betta fish pregnant is a very common one that people have been asking since bettas were first bred in captivity.
Bettas are not actually livebearers, instead, they lay eggs that develop into fry or baby fish once they become fertilized by a male betta. A female will typically produce anywhere from 5 to 500 eggs at a time. The male will make a bubble nest before mating begins and places each egg within it.
The betta mating process is quite interesting to watch, so I will describe the process in more detail throughout the rest of this post.
To get the most natural mating behavior, I recommend keeping your tank clean which you can read about here: How Often Do You Clean a Betta Fish Tank For Optimum Health.
I also have a water change frequency guide which you can read here: How Often To Change Betta Water – What you need to know.
Make sure to check out our Betta Fish Care Guide And Species Overview.
How Long Are Betta Fish Pregnant With Eggs
Female betta will generally carry eggs at all times until they are ready to release them. The eggs are fertilized as they sit in the bubble nest for between 24 and 36 hours. The female can lay a new batch of eggs every 48 to 72 hours until mating is complete, usually by mid-summer, depending on water conditions.
How Do You Know A Betta Fish Is Pregnant
As explained above, female betta will generally always carry eggs, so asking when a female betta is pregnant is probably the wrong term to use.
When a female betta is ready to mate, her stomach will look a little fuller where she may appear pregnant, and this is the perfect time to introduce her to a male betta, especially if the male has built a bubble nest ready to woo the female.
Often a fertile female will also develop white verticle stripes on her body when ready to mate.
How Many Eggs Do Bettas Lay
As a female betta can lay between 5 and 500 eggs at a time, a fuller pregnant-looking betta will have an abundance of eggs and can often mate for a second time very soon after the initial mating process.
What Do Betta Fish Eggs Look Like
A betta fish egg will look like a grain of salt with a slightly more transparent appearance. They can be easy to miss as they can often look like bubbles coming away from the female’s body as she releases eggs from her ovipositor.
How Do Betta Fish Mate
The betta mating process is wonderful to watch and very interesting to see how males and females interact.
There are several parts to the betta mating process, such as:
- The male betta will build a bubble nest.
- The male will then try to entice the female into his bubble nest.
- After this, he will nudge her in the area of the stomach where she is carrying eggs until she becomes receptive to mating with him.
- When she accepts him they begin “kissing” which involves the male biting the female betta on her dorsal fin.
- The female lays eggs which the male fertilizes and places in the bubble nest.
If you want to try breeding betta fish yourself, giving them the perfect environment with the perfect parameters is important, so setting up a betta tank the right way will be an important step.
The video below shows the betta mating process.
The male will begin by building a bubble nest, which he fills with air from his mouth until it is plump and round like a cotton ball. Once completed, the male betta can then try to attract females using unique patterns of fins quivering or flaring out.
Once a female betta is interested, she will approach the male, and he will follow her to create what looks like an underwater ballet. The two fish may circle each other for some time until they both begin to flare their gills and fins at one another before mating begins.
During mating, a male betta will wrap his body around the female’s to squeeze her and release eggs from her ovipositor, located underneath, in the space between the ventral or pelvic fin and the anal fin.
As the female drops her eggs, the male betta will swiftly grab them, spraying them with sperm to fertilize them and then placing the eggs safely in the bubble nest, which will keep them safe until they hatch.
As previously mentioned, female betta can release up to 500 eggs during one period of mating, so it is impossible to judge how long betta will mate for, but what I can say is that both fish may be quite exhausted afterward.
When mating has finished, the female may try to help the male put eggs into the nest; however, female bettas are also known to eat their eggs, so it might be wise to remove the female after mating and instead let the male take care of the nest.
How To Tell If Betta Eggs Are Fertilized
It is quite easy to tell if betta eggs are fertilized as they will have a black or grey dot inside of them. This is also a good sign if the dots are growing, and you can expect to see your new betta fry very soon.
Female betta will sometimes spawn or lay eggs that go unfertilized if they have not found a suitable male, and these eggs are often referred to as slugs.
Unfertilized eggs will often be eaten by either the female or an uninterested male.
How Long Before Betta Eggs Hatch
Betta eggs will usually hatch within 3-5 days of being fertilized by the male.
As the betta fry hatch from their eggs, they may drop from the bubble nest and will be unable to swim properly. The male will usually put them back in the nest to feed and grow until they are ready to swim by themselves.
If you are interested in breeding betta fish, I would highly recommend reading Baby Betta Fish (Care and Feeding Guide).
As you can see, the mating process of the betta fish is quite interesting, and there can be much back and forth hoping for a breeding pair to accept each other.
Once mating has occurred, it may be worth using a breeding tank to separate the male and female betta until the fry has hatched.
At some point after hatching, you might want to consider removing the male so there are no risks to the betta fry, and they can grow large enough to fend for themselves.