Mustard Gas Halfmoon Betta

Wherever they are found, Betta splendens generally inhabit shallow bodies of water with abundant vegetation, including marshes , floodplains , and paddy fields. The historic prevalence of rice farming across Southeast Asia, which provided an ideal habitat for bettas, led to their discovery and subsequent domestication by humans. The combination of shallow water and high air temperature causes gases to rapidly evaporate, leading to a significant deficit of oxygen in the betta's natural habitat.This environment likely led to the evolution of the lung-like labyrinth organ , which allows Siamese fighting fish—like all members of the suborder Anabantoidei —to breathe directly from the air. Subsequently, bettas can live and even thrive in harsher environments than other freshwater fish, which in turn leaves them with fewer natural predators and competitors. In the wild, bettas thrive at a fairly low population density of 1.7 individuals per square meter.

The tropical climate of the betta's natural habitat is characterized by sudden and extreme fluctuations in water availability, chemistry, and temperature. Water pH can range from slightly acidic (pH 6.9) to highly alkaline (pH 8.2), while air temperatures drop as low as 59 °F and rise as high as 100 °F. Consequently, Siamese fighting fish are highly adaptable and durable, able to tolerate a variety of harsh or toxic environments; this accounts for their popularity as pets, as well as their ability to successfully colonize bodies of water all over the world.