The wild Siamese fighting fish is native primarily to central Thailand and neighboring regions. Unlike the extravagant domestic strains seen in pet stores, wild Betta splendens display relatively short fins, metallic green scaling, and subtle red highlights. They inhabit shallow wetlands, canals, and floodplains where dense vegetation provides both shelter and spawning sites.
Splendens also includes every fancy Betta offered in pet stores.

Often called the Peaceful Betta, Betta imbellis is one of the least aggressive members of the complex. Native to southern Thailand and northern Malaysia, it displays brilliant iridescent blue-green coloration contrasted with vivid red fins. Its relatively calm temperament has made it a favorite among aquarists interested in maintaining small groups of wild bettas.

Known as the Emerald Betta, this species is famous for its brilliant metallic green scaling. Found throughout northeastern Thailand and parts of Laos, B. smaragdina inhabits rice paddies, ponds, and seasonal wetlands. Local populations often exhibit significant variation in coloration and patterning.

Discovered comparatively recently, Betta mahachaiensis is endemic to the coastal regions surrounding Bangkok. Unlike most members of the complex, it inhabits brackish nipa palm swamps and mangrove environments. This specialized habitat has made conservation of the species particularly important due to rapid urban development.

Described in 2012, Betta siamorientalis occurs primarily in eastern Thailand. It closely resembles B. splendens but differs in coloration, genetics, and geographic distribution. The species represents another example of how isolated populations can gradually evolve into distinct species. 

One of the least commonly encountered species in the hobby, Betta stiktos originates from Cambodia. It possesses a unique spotted pattern and remains relatively uncommon in captivity, making responsible captive breeding especially valuable. 

One of the most striking developments in recent years has been the emergence of the Alien Betta. Despite their wild appearance and metallic coloration, Alien Bettas are not a naturally occurring species. Instead, they are selectively bred hybrids developed by combining several members of the Betta splendens complex to create fish that exhibit the iridescent colors, bold patterns, and body shape associated with wild bettas while maintaining the vigor and variety of domestic strains.

Although individual breeding projects have differed, Alien Bettas are widely believed to have originated from crosses involving species such as Betta mahachaiensis, Betta smaragdina, Betta splendens, and, in some lines, Betta imbellis. Over multiple generations, breeders selectively paired offspring that displayed the desired metallic green, blue, or copper coloration, dark body pigmentation, and distinctive "armor-like" scaling that has become synonymous with the Alien Betta.

Unlike wild species, Alien Bettas do not represent a stable, naturally evolved population. Their exact genetic makeup can vary considerably between bloodlines depending on the breeder and the species incorporated during development. As a result, two Alien Bettas from different breeders may have noticeably different appearances, behaviors, and genetic backgrounds.

Species within the splendens complex adapt well to natural aquariums that mimic their native wetlands. Dense vegetation, floating plants, leaf litter, driftwood, and subdued lighting encourage natural behavior and reduce stress.

A varied diet consisting of live, frozen, and high-quality prepared foods supports both health and breeding condition. Insects, mosquito larvae, daphnia, bloodworms, and brine shrimp closely resemble the prey these fish consume in nature.

Although some species may coexist in carefully designed community aquariums, breeding pairs are generally best maintained separately to minimize territorial disputes.