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.
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.