Koi Nemo Betta (Betta splendens) is a domesticated form of the Siamese fighting fish, a species native to slow-moving freshwater habitats across Thailand, Cambodia, Laos, and Vietnam. Wild bettas are commonly associated with shallow wetlands, rice paddies, drainage ditches, floodplains, and densely vegetated waters where warm temperatures and surface access shape their behavior.

This selectively bred variety is known for its koi-style marbling, with shifting patches of orange, red, white, yellow, black, or blue that can continue developing as the fish matures. Like other bettas, it has a labyrinth organ that allows it to breathe atmospheric air at the surface, an adaptation useful in warm, low-oxygen environments.

Koi Nemo Bettas are bred for bold color, individual patterning, and display presence rather than wild-type appearance. They are best kept as a single showcase fish, where their color, surface-oriented behavior, and interactive personality can stand out in a calm, well-kept aquarium.