When most people think of bettas, they're thinking of betta splendens, or Siamese fighting fish. However, the term betta actually refers to dozens of different fish species.
Bettas are Territorial and Aggressive:
They're called Siamese fighting fish for a reason… bettas, especially the males, are territorial and will attack other male bettas (this isn't always "to the death," as commonly believed, although it can cause serious injuries). However, female betta fish can live together and male betta fish may be able to live with other species of fish.4
Bettas are Omnivores:
In the wild, bettas eat insects (crickets, flies, grasshoppers, etc.) and insect larvae, typically collected from the surface of the water, along with algae. They may also eat bloodworms, shrimp, or freeze-dried bloodworms.
Bettas Have Different Tail Shapes:
Part of what makes bettas so fascinating are their wide variety of shapes and colors. The tale shapes alone include comb, crown, delta, double feather, halfmoon, halfsun, plakat, rose, round, spade, veil, and more.
Wild Bettas are a Dull Brown and Green Color:
As mentioned, the vibrantly colored bettas you see in stores got that way through selective breeding. In the wild, bettas are a dull brown or green color and their fins are smaller and much more understated.
Males and Females are Easy to Tell Apart:
Male bettas are not only larger than females but they also tend to have brighter colors and more ornate fins. Most pet bettas are therefore male.
Bettas Breathe Air and Can Survive Out of Water for Short Periods:
Bettas have a special organ called the labyrinth organ, which allows them to breathe air from the surface. This is what allows them to survive in waters with low-oxygen content, such as shallow rice paddies, stagnant ponds, or even polluted waters.5 They can even survive outside of water for short periods, provided they're kept moist.
Because betta fish sometimes live in water with low oxygen, this doesn't mean they prefer it… and it also doesn't mean bettas should be kept in vases with flowers. Unfortunately, the idea that you can keep a betta in a flower vase is widely circulated, but this is not a healthy or humane way to house these fish.
Bettas Build Bubbles Nests:
Male bettas build bubble nests, and once the female releases the eggs (during an elaborate courtship ritual) the male gathers them in his mouth and "spits" them into the nest. Because creating bubble nests is an instinctive behavior, your betta will likely build a bubble nest even in captivity without a mate present.
Male Bettas Guard Their Offspring:
The male betta not only builds the nest, he also watches over the eggs until they hatch. The female doesn't participate and is, in fact, typically chased away by the male.
Bettas are Intelligent:
Betta fish can learn to recognize their owners and perform tricks, such as following your finger around the bowl, swimming through hoops, or pushing a ball into a goal.