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How Long Do Betta Fry Take To Grow & Reach Full Size?

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Betta fry tend to raise many questions, especially during the early stages of their lives. The one that often pops up is how long it takes for them to grow. Fortunately, after years of experience, I gained some knowledge on this topic.

It takes three to five months for betta fry to grow and reach full size. At this point, they are considered adults and have fully functioning scales and fins. However, only at the age of seven months will the betta reach sexual maturity and start reproducing.

As we move forward, I will elaborate on how long it takes for betta fry to grow, including a detailed table on different growth stages. Then, I will share a few tips that might make your betta fry grow faster.


A male betta fish that is taking care of its newborn fry.

Still curious? Feel free to check my complete guide on betta fish fry, where I discussed how to care for betta fry, what they eat, their growth stages, what equipment to use, and much more.

How Long Does It Take For Betta Fry To Grow?

This question doesn’t matter to most conventional aquarists. It makes no difference to them whether a baby betta grows to maturity in four months or a year. 

But if you want to sell your fish, the growth rate matters. If the betta fry can mature in the shortest period possible, you can move them out of the breeding tank, making room for more betta fry.

Under ideal circumstances, you can expect betta fry to reach adulthood within three months. Or, at the very least, they will exit the ‘Young’ stage within three months.

This table will help you understand the different betta fry growth stages more clearly:

EggDays 0-3
NewbornDays 3-7
JuvenileWeeks 1-3
YoungMonths 1-3
AdultMonths 3-5

Bear in mind that your male betta fry may become aggressive even before fully grown. As a rule of thumb, I suggest that you move them into a separate tank after eight weeks.

On a side note, the bettas should attain sexual maturity within seven months.[1] However, not every betta will follow the same schedule.

Some bettas will start mating after three months, while others will continue to grow for a year.[2] The growth rate will vary in response to the conditions in the tank. Poorly maintained tanks will either slow or stunt a betta fry’s growth. 

In the best-case scenario, the creatures will attain their maximum length, but it will take a few more weeks or even months. In the worst-case scenario, the bettas will remain small and infertile. 

In such situations, you are better off culling the bettas and starting anew. Even if the betta fry can reproduce, they may fill your aquarium with sick and deformed bettas.

A three-week-old female betta fish fry still hasn’t gotten its colors.

How To Make Betta Fry Grow Faster?

You don’t have to leave a betta fry’s growth rate up to chance. Professional aquarists use tools and techniques to make their baby bettas grow faster. They include:

1. Feed Your Betta Fry Properly

Food is probably the most crucial variable. The diet will shape a betta fry’s future, determining whether or not it even survives to adulthood. 

Keep the following in mind:

  • You don’t have to feed the fry for the first few days after they hatch, as the babies are still attached to their yolk sacs.

It is better to wait until the fry absorb these sacs and become free swimmers.[3] The male betta will watch over them during this period, keeping them protected within the bubble nest.[4]

Once you remove the male betta, it is your turn to feed the betta fry. Here is a table that shows what they eat at different ages:

InfusoriaUntil they reach day 7
Baby brine shrimpFrom day 7 to 21
Freeze-dried/frozen foodsFrom day 21 and beyond
BlackwormsFrom week five and beyond
Dry pelletsFrom week eight and beyond
  • When they are just born, the fry are tiny, and their mouths are too small to accommodate ordinary fish food, which is why most aquarists go with infusoria.

Infusoria is an excellent addition to a fry’s diet because these organisms are even smaller than brine shrimp. 

Infusoria ranges from 25µ to 300µm. That doesn’t seem all that impressive until you realize that 1 µm is the equivalent of 1/1000 of an mm. Brine shrimp is roughly 400µm.

You have to culture infusoria before the bettas spawn. According to the International Journal of Fisheries and Aquatic Studies, the process involves adding lettuce, banana peels, and cabbage to a freshwater aquarium.[5]

It can take a week or less to see the results under a microscope. Because infusoria is microscopic, you have to use a dropper to feed the fry. Siphon water with infusoria out of the container and squirt the stuff into the breeding aquarium.[6]

Feel free to check my complete betta fry feeding guide if all that sounds intimidating. I made sure to include a helpful video that demonstrates how to culture infusoria at home.

Three-day-old betta fish fry that are now free swimmers.
  • Wait at least a week before switching to baby brine shrimp. The baby brine shrimp can supplement the microscopic foods.
  • You can discontinue the microscopic foods after a week. At that point, the fry are too large to benefit from food items that small. You can continue with the baby brine shrimp.
  • Wait four weeks before adding bloodworms, daphnia, and other conventional meals. You have to grate them thoroughly to produce fine particles that can fit in the mouths of the babies.
  • Many aquarists prefer to wait until week nine before switching to dry pellets. 
  • Prioritize protein-rich food items. The size of the meals should match the size of the fish. 

Newborn fry require several meals a day. You don’t have to concern yourself with overfeeding during those early stages. Although, you have to change the water regularly to prevent the leftovers from choking the tank. 

  • Wait until the fry are three or four weeks old to add frozen and freeze-dried foods to the tank. Like everything else, you should crush the foods with a blender to produce the delicate texture that baby bettas can consume.
  • Experiment cautiously with commercial food. If the babies reject it, switch back to live food items like micro worms and bloodworms. If you prefer commercial foods, look for protein-rich products.

2. Give Your Betta Fry Enough Room

Despite what some people think, betta fry will not grow to fit the size of the tank. However, you are still expected to give these creatures as much room as possible. 

Aim for 20 gallons. Twenty gallons can accommodate as many as 150 babies, which is good because the average betta produces 40 to 50 babies. Of those, about 90 percent will survive if appropriately raised. 

Don’t make the aquarium too big. If you do, the fry may starve because they have to cross large distances to find food.

Recently born betta fish fry, still hanging to their bubble nest.

3. Make Sure The Water Conditions Are Right

This goes without saying. Poor quality water will stunt a betta’s growth. Most importantly, you have to maintain the appropriate temperature and pH. 

Aim for these water parameters:

  • Temperature: 85-88° F (29-31° C) 
  • pH: 7.0-7.2 
  • General hardness: 2-20 dGH (70-300 ppm) 
  • Carbonate hardness: 3-5 dKH (55- 90 ppm) 
  • Ammonia: 0 ppm  
  • Nitrites: 0 ppm
  • Nitrates: <20 ppm

To measure the pH, ammonia, nitrates, and nitrites, I personally use the well-known API FRESHWATER MASTER TEST KIT (link to Amazon).

After trying dozens of those, this one is probably the most accurate. It also lasts for eight hundred measures, making it highly cost-effective.

For the water hardness, I usually go with the API GH & KH TEST KIT (link to Amazon). It is pretty affordable and easy to use.

Test the water routinely and ensure that any changes to the parameters occur gradually. Suddenly swings in the pH or temperature could kill the fry. If they survive, the shock and stress will slow their growth drastically.

4. Perform Routine Water Changes

Even though the fry are small, they can still create a mess in the breeding tank. Don’t forget: you have to feed them several times a day. 

Therefore, you run the risk of saturating the tank with leftovers. Naturally, you have to install a filter, preferably one that won’t suck the fry in. But a filter is not enough. 

Even if you have the best filter in the world, you are still expected to perform regular water changes. Replace up to 25 percent of the water to keep the ammonia concentration under control.

5. Turn Off The Lights On Time

It might come as a surprise, but betta fry need to sleep. Like other types of fish, they require a few hours of complete darkness.

Exposing betta fry to too much light will stress them and stunt their growth. They may even be more vulnerable to diseases, including bacterial in parasitic infections.

As a rule of thumb, aim for 10 to 12 hours of light. That will create a proper day/night cycle, which is also what they would have gotten if they were to live in the wild.

This male betta fish has finished placing his egg in the bubble nest.

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Conclusions

It takes approximately three months for betta fry to grow and reach full size (about two and a half inches long). At this stage, they are considered adults and have fully functioning fins and scales.

At the age of six to seven months, they reach sexual maturity and can reproduce. So, if you don’t want any further generations, it is best to separate the males from the females at this point.

References

  1. https://www.tinyfishtank.com/why-is-my-betta-fry-growing-so-slow/
  2. https://nippyfish.net/2011/03/22/lifecycle-of-siamese-fighting-fish/
  3. https://unitedbettaworld.com/how-to-make-betta-fry-grow-quickly/
  4. https://pets.thenest.com/care-baby-fish-3542.html
  5. https://www.fisheriesjournal.com/archives/2016/vol4issue3/PartB/4-1-89.pdf
  6. https://biotopeone.com/simple-live-food-cultures-growing-healthy-betta-fry/