Siamese Fighting Fish

What is Siamese fighting fish?

The Siamese fighting fish (Betta splendens) is a freshwater tropical fish belonging to the family Osphronemidae, native to Thailand. They are widely recognized for the aggressive behavior of males toward one another, a trait for which they were historically domesticated for contests.¹²

In the wild, these fish are typically greenish or brown with modest fins, but selective breeding has produced varieties with long, flowing fins and vibrant colors like blue, lavender, and red. They are classified as labyrinth fish, a group known for their ability to breathe atmospheric air.¹

A fascinating aspect of their biology is their reproductive behavior: males construct a “bubble nest” at the water’s surface by coating air bubbles with saliva. The male diligently guards these eggs, catching them in his mouth if they fall and returning them to the nest to protect them from predators.³

What is a bubble nest?

A bubble nest is a collection of air bubbles created by certain species of fish to serve as a nursery for their eggs. This behavior is most notably observed among labyrinth fishes, such as the Siamese fighting fish.²⁴⁵

To construct the nest, the male fish swims to the water’s surface, takes in air, and coats it with a mucous secretion from his mouth before spitting the bubble out. This process is repeated until a cluster of bubbles forms, often among aquatic plants. Once the female lays her eggs, the male collects them in his mouth and deposits them into the bubble nest. The male then guards the nest, protecting the eggs from predators and ensuring they remain aerated until they hatch.⁴⁵

How do labyrinth fish breathe?

Labyrinth fish possess a unique dual-respiratory system that allows them to thrive in diverse aquatic environments. While they utilize gills to extract dissolved oxygen from water—much like most other fish—they also rely on a specialized supplemental structure known as the labyrinth organ.⁶⁷

This organ is located in a chamber situated above the gills and is richly supplied with blood vessels. It functions similarly to a rudimentary lung, enabling the fish to gulp air at the water’s surface and extract oxygen directly from it. This adaptation is particularly advantageous for species such as the Siamese fighting fish and gourami, as it allows them to survive in oxygen-poor waters or even briefly out of the water.⁶⁷

What are the best conditions for keeping a betta fish?

To keep a Siamese fighting fish (Betta splendens) healthy, it is important to replicate the conditions of their native Thailand. As tropical fish, they thrive in warm, clean freshwater environments.

Because they are labyrinth fish, they require access to the water’s surface to breathe atmospheric air. While they are hardy, they should be kept in an appropriately sized tank with stable water parameters and gentle filtration to avoid stressing their delicate fins. It is also essential to house them individually, as males are notoriously pugnacious and will fight if kept together.