Normal adult bettas are usually around 3 inches (7.6 cm) in length. Hold a measuring tape up to your fishes' bowl and see how long it is. If your betta is less than the average, your betta is most likely a juvenile.It can be hard to measure a betta exactly. In most cases, you will be enough to simply get an estimate by holding up a measuring tape next to your fishes' bowl.;
, Adult bettas have nice and beautiful flowing fins. If your betta has this characteristic, this is a good sign that it is an adult. If it has tiny fins, then it is either a juvenile or a baby.Older betta's fins have typically undergone lots of wear and tear. They may have tiny tears or shredded ends.
Make sure you know the sex of your betta. Female bettas never get long, flowing fins like the males do.
Don't confuse normal wear with injuries from diseases.
 In general, young bettas are vibrant and middle-aged bettas are slightly faded. The color of the scales of an older betta will be slightly faded and muted.


Bettas that are bred for pets come in a wide variety of colors. However, wild betta fish tend to be grey or dull colored, and only show flashes of color when fighting.
Check your betta's size.
Check your betta's fins.
Assess the color of your betta.
{"src": "wikihow-all_validation", "title": "How to Tell How Old a Betta Fish Is1"}