Betta fish have become the most famous species in the aquarium hobby and there are more than enough reasons. Their vibrant colors and energetic behavior in a tank make them a popular choice for most beginners but people often fail to realize one important factor – how big do Betta fish get?
Betta fish will grow depending on the environment and living conditions. A regular adult specimen in a small tank will reach about 2.25-2.5 inches in length while under the right conditions, some fish grow even bigger – up to 3 inches (7.62 centimeters).
However, how big should a Betta fish tank be? Will your Betta grow bigger if you give it additional space?
You can find the in-depth answers to these and other important questions about Siamese fighting fish in the following article. Continue reading below and become an expert in Betta fish care.
How Big Do Betta Fish Get?
You have probably heard the popular saying that betta fish growth is influenced by the size of the tank.
Well, this is nothing more than a myth and a wider aquarium will not make your Betta bigger.
That is like saying a puppy will stay small if you keep it in a box.
Many factors influence Betta fish growth that have little to do with tank sizes.
Of course, if you put it in a small bowl or a miniature aquarium, it might never reach its full potential.
However, this will happen because the environment will not be good enough for pristine health.
Generally, adult Bettas has an average size of 2.25 inches in length (about 5.5- 6 centimeters).
Depending on the fish and how you’ve cared for it, it can grow up to 3 inches (7.62 centimeters).
When you look at an adult male and a female Betta fish, it might appear like they are different in size – males usually get ‘bigger’ but that is the effect of the larger fins.
Generally, the bodies of both genders have the same size in adulthood but males often have thicker bodies.
Overall, Bettas are small fish and unless your one has some extreme genes, it will not grow beyond 2.5-3 inches in length.
This is one of the many reasons why Bettas are relatively easy to care for – once you set up a proper tank in the beginning, you won’t have to upgrade to a bigger one once your Bettas grow.
How Fast Do Betta Fish Grow? Betta Fish Life Stages
Generally, we can divide the life of a Betta fish into four life stages – egg stage, fry stage, juvenile stage, and adult stage.
With this said, how big do Betta fish get over the first weeks of their lives?
These will be discussed in more detail below, but this video by Bije Aquatics provides an excellent visual summary of betta fish growth and their life stages:
Depending on the temperature of the water, Bettas will hatch a few days after the eggs have been fertilized in the bubble nests.
Once the Betta fry appears, they do not look alike their adult parents.
Their tail is not visible at this stage yet and they are extremely fragile.
We mentioned the importance of hiding places several times above.
Remember to provide enough spots for them to hide and feed while they grow.
This stage of life begins as soon as the Betta fry begin to swim freely away from their egg sacs.
There is no way to know when this period will commence exactly but generally – around 2-3 weeks after birth.
There is no uniform answer as to when your Betta will become an adult but experts often explain that this happens around the 10th week.
At this point, the Bettas should be about 1.5 inches in length, which is more than half of their usual size.
Betta Fish Growth Chart
Here is a basic betta fish growth chart:
Growth rate (Weeks)
|Newborn||About 0.1 inch (0.25 cm)|
|Two weeks old||About 0.25 inches (0.63 cm)|
|Four weeks old||About 0.45 inches (1 cm)|
|Six weeks old||About 0.8 inches (2 cm)|
|Eight weeks old||About 1.3 inches (3.30 cm)|
|Ten weeks old||Above 1.5 inches (3.80 cm)|
How Big Do Bettas Get In The Wild?
The natural habitat of these fish is the shallow waters of rivers in Thailand, Indonesia, Malaysia, Vietnam, and southern China.
These are tropical areas; the water is warm, with temperatures above 26 °C.
If the water in the aquarium falls below 24 °C, the fish become apathetic and lose vitality. This is a major factor for Betta fish growth in a tank.
In the wild, however, Betta fish do not get much bigger.
On rare occasions, people have found wild Bettas that outgrew the standard 3-inch length but such specimens are rare.
In other words, with proper care, your Bettas will grow to the full size they reach in the wild.
Wild bettas don’t have the long, flowing fins of captive bred specimens.
There are also several species of betta fish besides Betta splendens (common aquarium betta fish).
Some grow twice as large, reaching up to 6 inches long!
How To Safely Make Betta Fish Grow Bigger
Here is a common misconception – fishkeeping is easy.
As someone who has had cats, dogs, and several aquariums – I genuinely believe that fish require the utmost attention.
You already know what to expect in terms of size.
However, Betta fish growth depends on the environment and your effort, like with any other species.
Here are a few subtleties that you should envision and provide for your Betta that will help it grow to its true size.
Give it space
Yes, a Betta fish will not outgrow the standard size of its species if the tank is bigger.
But will it ever grow at all if the tank is too small?
The common misconception about Bettas is that they can thrive in a small bowl or a small tank.
Think again! Such conditions will make the immune system of the Betta weaker and more susceptible to illnesses.
Moreover, these conditions will influence its growth.
Give your Betta at least 5 gallons (minimum) of space and watch it bloom.
Extra space also ensures that water quality remains good.
Smaller tanks tend to shift parameters faster than larger ones.
Standard fish flakes will keep your Betta alive but proper nutrition always makes a difference.
This species needs food that is high in protein.
Consider higher-grade products that have been made specifically for Bettas rather than the regular foods that pet stores sell for fish in general.
Freeze-dried foods are also a good alternative.
It is good to keep the diet diverse and nutritious. Consider purchasing freeze-dried brine shrimp or bloodworms.
However, make sure not to overfeed your Bettas.
Do not feed them in one go. Instead, give them small portions of food two or three times a day.
Overfeeding can influence health and growth.
Moreover, leftover food will influence water conditions.
A healthy environment equals healthy fish.
This is a fact for all fish species, not just Bettas.
Give it the closest conditions to its natural habitat, and your pet fish will show you its maximum potential in return.
Besides tank size, what else can you do to improve the environment?
Start with the temperature – keep it within the range of 24 – 30 °C or 75 – 86 °F.
Especially if you have a younger Betta, it will be sensitive to serious temperature changes.
Keep it around 28 °C (82.5 °F) and you will have one healthy Betta.
The easiest way to control temperature is with an internal heater.
There is a wide variety of affordable options out there, so this additional instrument will not affect your budget.
You must provide a natural day and night pattern for your Bettas.
This means that you need proper lighting for your tank.
Yes, Bettas can thrive with natural daylight but it is always good to have proper artificial lighting that you can turn on and off at the same time each day.
Make sure to place your tank in a place that doesn’t allow direct sunlight.
In other words, keep it away from windows – sunlight can have a serious impact on water temperature and tank conditions in general.
Natural sunlight is also an excellent way to begin an algae infestation.
Green water algae, green hair algae, and other problems are hard to cure if your tank gets any amount of direct sun.
While Bettas can survive in an unfiltered tank, it is always better to add a filter.
Especially if the tank is bigger than 5 gallons, I would say it is mandatory if you want to keep the water pristine.
Nothing helps with tank maintenance like a quality filter.
It will reduce the development of harmful bacteria and will help with oxidation and nitrification.
Keep in mind that Bettas are not strong swimmers.
A powerful filter can create strong currents and stress the fish.
Consider purchasing one that has adjustable power and use all available tools to reduce currents.
There are plenty of options on the market such as the AquaClear Fish Tank Filter, which is available in several sizes and is extremely affordable.
- Water conditions (pH, nitrite, nitrate, ammonia)
Besides temperature, you need to monitor nitrite, nitrate, ammonia, and pH levels at least monthly.
Beginners can find this difficult but it is important for fish health.
Bettas prefer acidic pH levels. Keeping the pH neutral at 7.0 will be ideal but your fish will thrive if the pH ranges between 6.5 and 7.5.
Consider purchasing a water test kit because the water you use for the tank may have higher or lower pH than necessary.
When it comes to ammonia, the ideal figure is 0 ppm (parts per million).
Nitrite should also be kept at a minimum while nitrate should generally be kept below 40 ppm.
Always use a water conditioner to remove toxic metals and maintain the pH levels.
Moreover, do not use distilled water as it does not contain the natural minerals that improve fish health.
- Water changes
Water cycling is mandatory and it does not matter if you have a filter or not.
Keeping the ecosystem clean will prevent illnesses and help the Bettas grow.
I mentioned it once already but be careful with food as leftovers create additional waste.
The longer you keep the tank with the same water, the more its quality declines.
Ammonia will build up even though you have a filter and the pH will reach unhealthy levels.
In time, you should get used to systematic water changes but if you are a beginner, try to do it as often as possible.
Generally, you have to change about 25% of the water 1-2 times a week.
Apart from that, we recommend a 100% clean water change at least once a month.
Remember to use a water conditioner and dechlorination drops for all water changes.
Also, do not take your Betta out of the tank during regular water cycling.
Of course, do it when you change the entire volume once a month.
Last but not least, always acclimate the Bettas if you remove them from the tank.
This is their home and they are used to that specific ecosystem.
Sudden changes in the environment can cause stress.
- Plants and hideouts
Last but not least, we should mention the importance of plants and hiding places for Betta fish.
Moreover, there are subtleties when it comes to decorating a Betta tank.
The natural habitats of this species include a wide variety of hiding spots – rocks, plants, woods, etc.
Furthermore, Bettas love a place to hide when sleeping.
Especially if you have more than one Betta – a male and a female, for example, places to hide are mandatory.
So, live plants or fake decorations?
Overall, fake plants can do the trick but there are a few things to consider.
Betta fish can get hurt if the decorations have sharp edges. Always get plants that have silk leaves instead of plastic.
However, consider getting live plants. Besides their obvious beauty, live plants improve water conditions and of course, they resemble the natural habitat of the fish.
FAQs About How Big Betta Fish Get
How big is a full grown betta fish?
The maximum growth for betta fish is usually somewhere around 2 to 3 inches in length.
But their size can vary a bit depending on things like their breed, genetics, diet, and care over their lifetime.
Some end up a little smaller or bigger.
Do betta fish grow in bigger tanks?
A spacious tank will give your bettas more space to swim around and be active, which supports their healthy growth and development.
The extra room reduces stress too.
So while their genes primarily determine their size, a roomy tank can help them reach their full potential.
How long until a betta fish is fully grown?
It takes around 4 to 6 months for a betta to fully mature.
But factors like nutrition, genetics, and care as a juvenile affect how quickly they grow. With high-quality food and care from a young age, some may reach adult size a little faster.
How big should my betta fish grow before they can breed?
With high-quality care, most bettas will probably be developed enough to breed around 3 or 4 months old, when they reach about 1.5 to 2 inches long.
However, there isn’t a magic number for size that means a betta is ready to breed.
It’s really about the fish being mature and in good condition overall.
The most important thing is that the fish are healthy and ready, not just meeting some particular length.
Whether you landed on this page as a beginner or an experienced hobbyist in search of a specific answer, we covered everything related to Betta fish growth.
You now know what to expect from your Bettas throughout their entire growth cycles.
You also know how to improve their environment in various ways that can boost your fish’s health and growth.
One last tip before we go – Bettas are so common nowadays that you can find them everywhere but most pet shops do not provide the necessary care or environment.
Our recommendation is to buy your Bettas from certified pet stores that are dedicated to fishkeeping rather than just a regular pet store.
- Frequently Asked Questions About Betta Fish – 37 Things You Must Know
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- How To Transfer Bettas From Cup To Tank – Find The Details Here
- Can Two Betta Fish Live Together? See The Determining Factors Here
- How Often Should A Betta Fish Tank Be Cleaned? Cleaning Guide