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The Life Cycle of Siamese Fighting Fish

Betta splendens, bettas or so-called "Siamese fighting fish," are surface air-breathers second only to goldfish in popularity. These unique freshwater fish pass through several life stages on their way to becoming the long-finned specimens you meet in pet stores. Very young bettas need more food than adults and scrupulously clean conditions. Adult bettas are very easy to care for and can live to be around 3 years old or older with proper care.

Parental Romance

The life cycle begins with the parents' romance -- which is exceedingly brief and potentially dangerous. Males are notoriously aggressive to each other, other long-finned fish and even females of their own kind. Males and gravid females get along for a few minutes while they're breeding. They intertwine, the female deposits roe (eggs) onto the male's tail and he deposits milt (sperm) on top of them. Dad picks the eggs up with his mouth and gently moves them to the bubble nest he's built for this occasion. Then he chases the female away and may attack or even kill her if she isn't removed from the tank.


The eggs hatch within 36 hours. Baby bettas stay in their nest until they've absorbed their yolk sacs at about 5 days of age. At this point either Dad or the babies have to be moved out to prevent an attack on the babies. This is called the free-swimming or fry stage -- the young have moved out of the nest, but they're still babies until their gills are replaced by labyrinth organs at 3 to 6 weeks of age, allowing them to breathe surface air. Fry need to eat many times per day, and their food is nearly microscopic. Feeding new babies requires culturing a variety of invertebrates called infusoria.


Juvenile or adolescent bettas have fully-developed labyrinth organs, but immature sexual ones. Their fins continue to grow and their colors may change dramatically until they reach sexual maturity at around 3 months of age. Their behavior may change during this time as well, as they begin to seek out territories and become steadily more aggressive to their own kind and similar-looking fish.


Bettas become fully adult between 3 and 12 months of age. By the 1-year mark they're sexually and behaviorally mature; they must be kept away from other members of their own species and other long-finned or nippy fish, they'll need only one meal per day, and their fin length and colors will be relatively stable, though colors may fade or change slightly as they reach old age. The normal life expectancy for a well-cared for betta is about three years.

Betta Care Myth-Busting

Contrary to pet store displays, a betta can't live in a dirty tea-cup-sized bowl. Like other fish, bettas need a minimum one gallon of water per inch of fish. Filters and aeration devices are a no-no. They need several inches of gravel, live plants and a tank cover. Water at 75 to 80 degrees Fahrenheit is ideal. If your house gets colder than this, you'll need an underwater heater and thermometer. Do a 25 to 50 percent water change with a gravel vacuum and water conditioner at least twice a month. Adult bettas need specially formulated betta pellets or appropriate live food once per day. Always follow food package instructions.