Breeding betta fish can be an exciting and rewarding experience for any aquarist. After conditioning your pair and helping them spawn, the next step is determining whether the eggs are actually fertilized and viable.
This guide will walk you through everything you need to know about identifying fertilized betta eggs, so you can successfully hatch out a new batch of baby bettas.
If you’re short on time, here’s a quick answer to your question: Look for opaque, round eggs approximately 1 mm in diameter, and watch to see if the male is caring for the nest. Fertilized eggs will turn darker over 24-48 hours, while unfertilized eggs will turn white and fungus quickly.
In this comprehensive article, we’ll cover signs like egg appearance, male behavior, development rates, and more to help you confidently identify healthy, fertilized betta eggs.
Examining Egg Appearance and Size
Fertilized eggs will be round and opaque
When betta fish eggs have been successfully fertilized by the male, they will take on a spherical shape and become opaque in color. The fertilized eggs will appear white or cream-colored, with a yolk clearly visible inside each egg.
This round, opaque appearance indicates that the eggs have been penetrated by the male’s sperm and cell division and embryo development have begun inside the eggs. Keep an eye out for eggs that fit this description to identify which ones have likely been fertilized after spawning.
Unfertilized eggs look irregularly shaped and transparent
In contrast to fertilized betta eggs, unfertilized eggs that did not get successfully penetrated by sperm will fail to become fertilized. These unfertilized eggs tend to have an irregular, oblong shape instead of a perfect sphere.
Additionally, unfertilized eggs remain transparent, with a wispy, translucent appearance instead of an opaque white/cream color. If you notice eggs that are misshapen and see-through rather than round and opaque, chances are those eggs were not fertilized and will not hatch into baby betta fry.
Newly laid eggs are very small, about 1 mm in diameter
Right after the female betta releases her eggs during spawning, the eggs will be extremely small, with a diameter of only about 1 mm. That’s just a bit bigger than the head of a pin! So don’t expect to see large, prominent eggs immediately after the mating ritual.
You’ll need to look closely to spot the tiny new eggs. Within a day after spawning, the fertilized eggs will swell up to 2-3 times their original size due to water absorption, making them more visible. But when first laid, all betta eggs are tiny, fertilized or not.
Use a magnifying glass if needed to observe the newly spawned eggs closely.
Watching the Male Care for the Nest
When betta fish eggs have been successfully fertilized, the male betta will diligently tend to the nest. On the other hand, if the eggs are not fertilized, the male will lose interest in caring for them.
The male will tend fertilized eggs, retrieving fallen ones
A male betta fish is an extremely devoted father. After spawning, he will carefully gather the fertilized eggs and place them in the bubble nest he has built. He will attentively monitor the eggs in the nest, retrieving any that fall out and putting them back into the nest.
It’s amazing to watch him meticulously care for the hundreds of tiny eggs!
The male betta understands the importance of keeping the eggs together in the nest and oxygenated. If he notices an egg drop from the bubble nest, he will promptly swim down, gently pick it up in his mouth, and return it to the nest.
He may spend several hours each day tending the nest and retrieving fallen eggs. What a dedicated dad!
He won’t care for unfertilized eggs and may eat them
In contrast to fertilized eggs, the male betta will completely ignore unfertilized eggs. He seems to instinctively know which eggs have not been fertilized and will not bother putting any effort into caring for them.
Not only will he not tend to unfertilized eggs, but he may even devour them! This may seem surprising given how attentive he is to the fertilized eggs, but eating the dead eggs helps keep the nest clean.
So don’t be alarmed if you see your male betta nibbling on some of the eggs from the spawn—chances are, they were never fertilized to begin with.
The difference in the male’s behavior is a clear sign of whether eggs have been successfully fertilized or not. If he is fastidiously tending to the bubble nest, you can rest assured the eggs are fertilized.
But if he loses interest and starts snacking on them, fertilization unfortunately did not occur.
Monitoring Egg Development and Changes
One way to determine if your betta fish eggs have been successfully fertilized is to observe them carefully over the first couple of days. According to experts, fertilized eggs will gradually darken and change color within 24-48 hours after spawning.
The eggs may take on a darker brown, gray, or black hue during this timeframe. This darkening occurs as cell division and embryo development starts inside the fertilized eggs. If you notice this steady color change, it’s a positive indication that viable embryos are forming.
Fertilized eggs will get darker over 24-48 hours
In contrast, unfertilized betta eggs that do not get darkened and fertilized will remain light-colored. According to research on the Betta Source forum, these unfertilized eggs often turn white or opaque. Additionally, they tend to develop fungus more quickly compared to healthy fertilized eggs.
You may observe fuzzy mold beginning to cover the surface of opaque white eggs within a couple days. This fungus growth signals that no embryo formed, indicating the egg was unfertilized and nonviable.
Checking for this white color change and fungus spread can help confirm if fertilization failed to occur.
Unfertilized eggs turn white and fungus quickly
Noticing Hatch Rates and Timing
When it comes to determining whether your betta fish eggs are fertilized or not, keeping an eye on hatch rates and timing is crucial. Here’s what you need to know about what to expect if you have fertilized eggs:
Fertilized eggs will hatch in 24-36 hours typically
If the eggs have been successfully fertilized by the male betta, you can expect them to hatch within 24-36 hours typically. Once the fry hatch, they will be tiny little fish, usually less than 3 mm long. They may still have some yolk sac attached at first.
The egg casing splits open and the fry emerges head first when hatching.
Some key signs that the eggs are fertilized and developing normally:
- Eggs look plump and opaque white in color
- After 12-24 hours, you see little black dots inside the eggs (developing eyes)
- Just before hatching, eggs may turn darker and you’ll see the shape of the fry moving inside
If the eggs stay small, clear and translucent, that’s a good indication they were not successfully fertilized.
Infertile eggs won’t develop or hatch
On the other hand, if the eggs are infertile and haven’t been fertilized, you’ll notice very different signs. Infertile betta eggs typically:
- Remain small, clear and translucent
- Don’t enlarge or become opaque
- Show no signs of embryo development inside
- Will eventually get a white fungal coating and decompose
Infertile eggs simply won’t progress to the hatching stage. After 3-4 days, they will start to whiten with fungus and break down. Removing infertile eggs promptly helps keep the water clean.
According to The Betta Fish Site, the hatch rate for healthy betta fish eggs can be 80% or higher. So if less than 50% of your eggs hatch, it may indicate an issue with the breeding pair or aquarium conditions.
The bottom line is fertilized betta eggs will normally hatch within a day or two. Keep a close eye on the hatch timing and progression. This will let you know if your eggs are developing healthy fry or not.
With a little experience, you’ll learn when to expect the exciting moment of little betta fry emerging!
Removing Unfertilized Eggs
Unfertilized eggs can fungus and infect good eggs
It’s crucial to promptly remove any unfertilized betta eggs from the tank, as they can quickly develop fungus that spreads to healthy eggs (not awesome!). Unfertilized eggs turn white and opaque within a day or two, making them easy to identify.
Using a siphon or tweezers, gently remove these bad eggs right away before they decay further. An article on the Betta Source website notes that leaving dead eggs in the tank provides an opening for dangerous fungal or bacterial blooms to occur.
Use a siphon or tweezers to remove bad eggs daily
Check for and eliminate unfertilized eggs from the tank every day. A good method is using an aquarium siphon during partial water changes. Place the siphon end near white rotten eggs and gently suck them up through the tube. Aquarium tweezers also work well for egg removal.
Simply pinch the dead eggs to pull them out. Whichever tool you use, take care not to disturb healthy eggs during the process. Consistently removing unfertilized eggs improves odds for the remaining eggs to hatch and reduces disease risk (đź‘Ť).
An article on Bettafish.org recommends inspecting eggs twice per day if possible.
Conclusion
Determining if your betta eggs are fertilized is important for the health of the spawn. Pay close attention to appearance, male behavior, development rate, and hatch times to identify viable embryos. Remove any fungus-covered duds right away.
If you follow these tips, you’ll be able to confirm fertilization and keep your spawn safe and healthy. With a good hatch rate, you’ll soon have lots of tiny betta fry to care for and enjoy watching grow. Congratulations on a successful betta fish spawn!
We hope this comprehensive guide gave you all the details you need to confidently identify healthy, fertilized betta fish eggs. Let us know if you have any other aquarium breeding questions!
