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Do Betta Fish Grow? How Big?

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Yes, the betta fish or Siamese fighting fish is a freshwater tropical fish that does grow as it becomes older. Betta fish are considered fully developed once they reach approximately 7 months old but can grow larger depending on their environment and care.

If you purchased your betta from a pet store, they are generally between 6 months to 1 year old. These bettas (usually betta splendens) may already be close to their maximum size and have likely fully developed their beautiful long finnage. Age, finnage, and size may vary if purchasing from a breeder or if it is another species of betta altogether (e.g. wild).

Certain pet stores like Petco have also begun selling baby betta fish (Fry). These juvenile bettas range anywhere from five weeks old to nine weeks old. Baby bettas are obviously much smaller in size and require special care and monitoring and should be reserved for experienced caretakers.

Betta Fish Growth Chart
Source: Wayne’s Betta Pages

How Big Do Bettas Get

Betta fish have an average length of 2.25 inches (5.7 cm) when they are fully grown. On occasion and under the right conditions, a betta fish can grow to as big as 3 inches (7.6 cm) in length. How large your betta will grow will ultimately depend on its age and how it has been cared for. The average life span for a betta fish is 2 to 4 years in captivity.

Adult male and female betta fish also differ in size if you take finnage into account. Males possess larger fins than females, however, their bodies at adulthood are generally the same size (average length). A male’s fins simply make them larger and longer in overall appearance. Males also tend to have thicker bodies than females.

How to Make Your Betta Fish Grow Bigger

Pet stores keep betta fish in small cups because they cannot be housed together and the shelf space for that many tanks isn’t usually possible for one aquatic species. Betta fish also do not grow to the size of their tank, however, if you want your betta to grow to its maximum potential you should provide a habitat that’s at least 5 gallons for him or her to thrive in.

Despite being relatively hardy fish, betta fish are also susceptible to many common aquatic diseases. To ensure maximum growth, you should limit stressors that can lead to premature death. Keep your water quality pristine (filters help) and make sure your tank’s water is within the tropical range of 76 to 82 degrees Fahrenheit. Internal thermostat heaters that maintain a temperature of 78 degrees Fahrenheit are ideal.

A diverse diet consisting of protein rich foods will also help to increase the size of your betta. Betta fish are carnivores and should be fed a mixture of high quality protein-rich betta pellets and freeze-dried bloodworms or brine shrimp. You may also consider live foods to further replicate their natural habitat, although live foods may carry disease.

Promoting a healthy environment will promote the longevity and overall size of your betta fish. Betta fish grow and thrive when they are healthy. If you have any other tips or recommendations, please add them in the comments below.

About the author

Hey, I'm Bryan (founder of bettafish.org) and I’ve been caring for and keeping betta fish for over 9 years. I’d like to extend you a warm welcome to the best community and informational place to learn all about this wonderful tropical, freshwater fish.

32 thoughts on “Do Betta Fish Grow? How Big?”

    • Males CANNOT be kept together at all …. never, but females can be kept in a sorority which is 3 female bettas or more, females have a calmer mindset, if you get female bettas it’s better to buy them in the same size and close to the same age to decrease chances of fighting. If more then one, they cannot live in a tank smaller than 10 gallons because bettas need their space from each other. They might bully each other to establish dominance but that’s why you get them in the same size and age if possible, hopefully, this will achieve a thriving sorority of bettas, if one bullies the others too much it would be best to remove it.

      Reply
  1. I have an adult red veil tail in a 5 gallon aquarium. I just got a baby Betta and I currently have him in a 1 gallon tank. I want to upgrade that as soon as possible. He’s currently blue with red fins. So cute.

    Reply
  2. I have a male king Betta, dispite many people saying his breed is more aggressive, King bettas are actually quite shy and calm, I’ve had him with my brothers school of fancy guppies and he just hid from them. But he’s in his own 5 gallon now. Any breeding tips? I was wanting to breed him with my grey and white elephant ear female marshmallow.

    Reply
    • I will be working on a breeding section for the site in the future. You can email me directly if you’d like and I can provide some resources for now.

      Reply
  3. Male bettas, depending on their personality, can certainly be kept in tanks with other fish!

    I have a 10 gallon tank with my red veiled betta, three fancy male guppies, and one albino cory catfish, and they’re all quite happy with each other!

    When I introduced the guppies to my betta he did flare at them and chase them around a bit for the first day, and that’s quite normal since the fancy male guppies can look similar to another male betta bc of their brighter colors. My betta quickly realized they weren’t a threat and now they all reside together peacefully.

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  4. What is the best substrait for male bettas? I’ve seen pictures showing small stones, tiny colored pebbles, and glass discs. Also, I was surprised to see drift wood in tanks. Is that safe?

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    • Aside from trying to mimic their natural habitat as much as possible, it’s an individuals preference as long as the substrate is safe for aquarium use. I prefer sand or aquarium gravel. Drift wood is safe if it’s sold for aquariums only – driftwood you find on the beach is not recommended as it likely contain a lot of harmful or deadly bacteria for your fish.

      Reply
  5. I have an odd, color changing delta. In some lighting its metallic sky blue with pink ends and silvery fins, but in other light its gold, dark silver with violet ends. Its only about an inch long and i cant seem to get it to eat anything other than small shrimp, he refuses to eat blood worms, pellets and anything else. Is that normal, not wanting to eat anything else? Ive had a few others but they all ate pellets and blood worms. Will he stop growing if he doesnt eat anything else?

    Reply
    • Some can be very, very picky Jay. I’ve had some that wouldn’t touch bloodworms and others who scoffed at almost every pellet. He won’t stop growing, but the greater concern is for diversity of diet and ensuring he is getting the appropriate nutrition of protein, fat, fiber and vitamins. If you haven’t yet, please check out my food and feeding guide to see if a different pellet or even flakes might be worth trying out. You can also try dipping a pellet in a little bit of garlic juice – just enough extra flavor to entice them to eat it. This isn’t a long-term fix but might get him in the routine of eating pellets as you phase out the garlic.

      Reply
      • Thank you for the info, i’ll be changing his diet as the pellets i bought have a lot of filler, i tried the garlic juice trick but he seems to have figured it out and ignores his food again. He is on a feeding schedule, and it may just be stress as he has a new home so im hoping its temporary. Thank you for the help and hopefully i can update with better news.

        Reply
  6. I have some betta fish but they’re all in the same tank they don’t fight I have a blue one or red white and blue one and I have a brown one and a couple other brown ones but they’re babies and then I also got another one named Oscar

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  7. I got a female betta approximately a month ago, while she wasn’t being sold as a baby (they don’t sell baby bettas here) she was by far the smallest betta I’ve ever actually seen. Even amongst the other females she was the smallest, now she lives in my 30 gallon planted community Blackwater tank (and has taken quite the liking to eating my pest snails) I can’t wait to watch her grow to her full potential. ☺

    Reply

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