Most fishkeepers will be able to tell you what a Siamese fighting fish looks like, but not many can tell you about their origins. Rodrigo takes a trip to Thailand to investigate their native range.
The first time I visited Thailand, I was immediately struck by the sheer biodiversity in every body of water. I went there on holiday, but as an aquarist, it was impossible to resist looking into every pond, stream, and flooded field I came across.
At the time, I had not done any research on Thailand’s native fish species or their habitats, nor did I have any underwater filming equipment with me. It quickly became clear that I had to return, this time properly prepared.
I eventually decided that my first target would be the beautiful bettas. The fighting fish is one of the most iconic aquarium species and certainly the most popular fish in Thailand. However, it turns out that the gorgeous, colourful bettas we see in the stores labelled as Betta splendens are actually likely to be a hybrid between multiple Betta species, such as Betta imbellis, Betta mahachaiensis, and, of course, B. splendens.
A male Betta splendens swimming alongside croaking gourami - all photos by Rodrigo Silva
For this article, I will focus exclusively on where the true B. splendens that every aquarist will have heard of comes from, diving deep into the hidden world it inhabits.
Related article: Finding the endangered Somphong’s rasbora.
The natural habitat of Betta splendens
Betta splendens, or simply fighting fish as many aquarists know them, are highly adaptable, thriving in a variety of habitats such as rice fields, flooded plains, irrigation canals, ponds, swamps, and even slow-moving streams.
During my visit, I explored a marshy wetland in central Thailand, about an hour north of Bangkok, nestled among farmlands. This area included deeper ponds, irrigation canals, and ditches that flood during the rainy season.
During this time, B. splendens move into these recently flooded, very shallow, grassy fields and ditches, making it an ideal spot to find them. However, catching a glimpse of one is no easy task.
These fish are some of the most elusive I have ever encountered. As soon as I approached the water, they quickly retreated into the grasses, dense vegetation, and leaf litter, staying hidden for extended periods.
These bettas clearly prefer these areas with abundant vegetation, so what plants can be found in this habitat? The most common plant was the Chinese water chestnut (Eleocharis dulcis), which grew along the margins, poking out of the water and creating a dense forest perfect for hiding.
Golden bladderwort (Utricularia aurea)
The second most prevalent plant was the golden bladderwort (Utricularia aurea), a carnivorous plant that grows suspended in the water column. There were also water lilies, possibly Nymphaea rubra and Nymphaea nouchali, though without flowers, I couldn't be certain. Sacred lotus (Nelumbo nucifera) was also present in the ponds.
Below the surface, there was a long-leafed plant that, at first sight, resembled Vallisneria. From my observations, it appears to be hydro-perennial and grows in a rosette; therefore, I am more inclined to say it is likely a Blyxa. It also has veins running down the middle of its leaves, which attenuate to narrowly acute tips, matching the description of Blyxa aubertii. Either way, plants such as Blyxa spp., Vallisneria spp., or Cyperus helferi all certainly seem like suitable options for a biotope-inspired aquarium.
Watch as our editor builds a planted aquarium for a domesticated Betta splendens inspired by the long grassy habitats featured in this article.
The wild Betta
Hidden among the grasses and aquatic plants along the margins of the wetland, there was a plethora of fish, including the very elusive bettas. The wild fish differ significantly from the domesticated breeds commonly seen in pet stores.
One of the most notable differences is their ability to drastically change colour. Unlike the vibrant reds and blues that you might expect, most wild male bettas I photographed were dull brown, with some displaying horizontal stripes for camouflage. It’s only when attracting females, defending their territory, or warding off other males that they flash their brighter colours.
In contrast, domesticated specimens have been selectively bred for vivid hues, deep blues, reds, purples, and even metallic shades. Some mutations have resulted in long, flowing fins, like halfmoons and crowntails. While these varieties are stunning, the exaggerated fins hinder movement, making them slower and more prone to injury, something that would not be advantageous in the wild. Wild bettas, with their shorter fins, are far more agile and resilient.
On rare occasions, I filmed multiple wild males swimming together peacefully, an unexpected behaviour for a “fighting” fish. This was particularly common with younger males, who often formed small groups, sometimes even mixing with the females. In one instance, I observed a B. splendens swimming alongside a group of croaking gouramis (Trichopsis vittata). These fish seem to be far more social than we make them out to be.
Domesticated bettas were originally bred for fighting in Thailand and other Southeast Asian countries. Consequently, they have been selectively bred for their aggression as well as those vibrant colours. These breeds are known to fight to exhaustion or even death. Even non-fighter breeds tend to display more aggression than their wild counterparts due to previous generations of selective breeding.
Wild B. splendens, however, are much less aggressive. Their fights are brief and rarely result in serious injury. They will flare, chase, and nip, but typically one retreats before any real harm is done, something they are unable to do in the confines of a glass box.
The contrast is even more striking with the females. Many viewers of my videos initially mistook the wild females for croaking gouramis, as they are fairly similar and completely different from the domesticated varieties. Wild female bettas are pale brown, much smaller than the males, and almost always display horizontal stripes. Interestingly, when I introduced a few wild females into an aquarium, their stripes disappeared within days, only reappearing when they were startled, such as during tank maintenance.
Wild females tend to form small groups and are far less shy than the males. I was able to capture much more footage of the females than the males. Some even seemed curious about the camera, investigating it as if they were interested in what I was doing.
One fascinating behaviour I observed in the wild was how bettas rise to gulp air from the surface in synchrony. They all swim up from beneath the vegetation and debris at the same time, and then quickly retreat into hiding. This coordinated action increases their chances of survival, protecting them from predators both above and below the water. Underwater predators include snakeheads, climbing perch, catfish, and reptiles, while above the surface, kingfishers, egrets, and herons all pose a threat.
Betta breeding behaviour
As you may know, B. splendens are bubble nesters, and so are many of the species in this habitat, such as the croaking gouramis and three-spot gouramis (Trichopodus trichopterus). I found many nests hidden among the marginal grasses in very shallow waters, sometimes only about 5 cm (2 in) deep. It was difficult to determine whether these nests belonged to B. splendens or one of the other bubble-nesting species.
Croaking gouramis under a large bubble nest
However, I did witness some breeding behaviour in the wild. On one occasion, I filmed a female displaying vertical breeding stripes, which is a sign she was ready to spawn. When a female is ready to mate, her body darkens to a deep brown, and pale vertical stripes appear. Her colours intensify, with hints of blue and red, and the red markings over her operculum become visible.
On another occasion, I witnessed a male chasing a female. Though the footage was unfortunately out of focus, it was still incredible to witness this behaviour in the wild. The courtship was so different from the aggressive displays seen in tanks, where the male pursues the female relentlessly. In the wild, with almost unlimited space, the courtship is more like a synchronised dance. The male follows the female, flaring his fins and displaying his brightest colours. As they swim, they make stops in perfect unison, creating a beautiful choreography.
The dry season
The dry season presents the most challenging conditions for wild bettas. Many of the flooded grasslands where I filmed will dry up, and while some fish can make their way back to permanent bodies of water, others may become trapped in smaller ponds or puddles, where the water quality begins to deteriorate. This is when their labyrinth organ proves invaluable.
By gulping air directly from the surface, they can survive in environments depleted of oxygen. Bettas are even capable of burying themselves in the mud at the bottom of dried-up habitats, where they can survive for short spells, even when thick, wet mud is all that remains of the water. However, they cannot survive in a completely dry habitat, so some will perish during the dry season.
Human activities have made survival even more difficult for wild bettas. The artificial drainage of wetlands for agriculture prevents them from finding shelter during these harsh dry months. As these suitable habitats shrink, the odds of survival for wild bettas become increasingly slim.
The other species found here
You might be wondering what other species share the same habitat as B. splendens. Well, there’s plenty. I observed the following during my time filming in this habitat:
- Croaking gourami (Trichopsis vittata)
- Dwarf medaka (Oryzias minutillus)
- Least rasbora (Boraras urophtalmoides)
- Red-tailed rasbora (Rasbora borapetensis)
- Striped snakehead (Channa striata)
- Climbing perch (Anabas testudineus)
- Giant snakehead (Channa micropeltes)
- Three-spot gourami (Trichopodus trichopterus)
- Malayan leaf fish (Pristolepis fasciata)
Dwarf medaka swimming above decomposing leaf litter
The current status of Betta splendens
The wild form of B. splendens is becoming increasingly rare. While feral populations of bettas can be found around the world, especially in other Southeast Asian countries, the pure wild form is in serious decline.
As of now, they are listed as Vulnerable on the IUCN Red List. The species faces numerous threats that have caused their populations to steadily decrease, primarily due to urbanisation, land conversion, and industrial agriculture, all of which contribute to the shrinking and pollution of the wetland habitats that these fish depend on.
In the past, B. splendens could even be found in the heart of Bangkok, but those habitats have long since disappeared. Rice paddies, once a vital stronghold for wild populations, have been impacted by modern farming practices and the use of pesticides. Artificial drainage has also disrupted the natural wet/dry cycles that are crucial for the fish's survival, while swamps and floodplains are being drained for agriculture and urban development.
You can watch Rodrigo's video of the habitat here, and make sure you subscribe to Practical Fishkeeping magazine so you don't miss future fascinating habitats that Rodrigo explores.
This was first published in the April 2025 issue of Practical Fishkeeping.