Species description

Care, breeding and tankmates

Fish profile

Temperament

Aggressive

Male Koi Galaxy bettas exhibit highly aggressive and territorial behavior towards other males of their own species and similar-looking fish. They are solitary by nature and will actively flare their gills and attack intruders to defend their territory. Despite their aggression towards conspecifics, they can be relatively peaceful or indifferent towards distinct, non-threatening species in a community tank. Females are generally less aggressive but still territorial and may establish a strict dominance hierarchy if housed together.

Diet

Carnivore

In their natural habitat, Betta splendens are carnivores, feeding primarily on aquatic insects, larvae, and other small invertebrates. In captivity, they should be fed a high-protein diet consisting of specialized betta pellets or flakes as a daily staple. To ensure optimal health and enhance their vibrant Koi colors, this diet should be supplemented with live or frozen foods such as bloodworms, daphnia, and brine shrimp. Overfeeding must be avoided, as bettas are prone to bloating, constipation, and swim bladder issues.

Life expectancy

3-5 years

In captivity, Betta splendens var. Koi generally has a lifespan of 3 to 5 years when kept under optimal conditions. Their longevity is strongly influenced by water quality, genetics, diet, and stress levels. Providing a heated, filtered, and well-planted environment will help them reach their maximum lifespan. It is important to note that many bettas sold in pet stores are already 6 months to a year old, which affects their remaining life expectancy.

Sex ratio

Group

Domesticated male bettas, including the Koi Galaxy variety, must always be kept individually because they are extremely territorial and will fight to the death. Female bettas are slightly less aggressive and can sometimes be kept in a group, often referred to as a "sorority," though this requires a large, heavily planted tank and experienced care. Keeping a male and a female together long-term is not recommended, as the male will harass the female constantly outside of spawning. Therefore, the standard stocking recommendation for a home aquarium is a single male or female per tank.

Feeding frequency

Twice daily

It is recommended to feed adult bettas once or twice a day, providing only what they can consume in about two minutes. Because of their small stomachs, which are roughly the size of their eye, offering small portions prevents digestive complications. Fasting the fish for one day a week is a beneficial practice that helps clear their digestive tract and reduces the risk of constipation. Juvenile bettas, which are still growing, may require smaller feedings spread out three to four times a day.

Bioload

Low

The biological load of a single Betta splendens var. Koi is relatively low due to their small size and solitary nature. However, because they are frequently housed in smaller aquariums (such as 5 to 10 gallons), waste products like ammonia and nitrates can accumulate rapidly. Adequate biological filtration is essential, but it must not generate strong water currents that would exhaust the fish. Weekly water changes of 20-30% are critical to maintaining pristine water quality and preventing health issues like fin rot.

Flow

Stagnant

Bettas naturally inhabit slow-moving or stagnant waters, such as rice paddies, swamps, and sluggish streams, and thus strongly prefer very weak water flow. High-flow environments force them to swim constantly against the current, which quickly exhausts them, damages their delicate fins, and causes chronic stress. A gentle sponge filter or an adjustable hang-on-back filter baffled with sponge is ideal for keeping the water clean without generating current. Floating plants can also be used to help diffuse any remaining water movement at the surface.

Jump risk

Yes

This species presents a very high jump risk, as they are capable of launching themselves out of the water, often when startled or chasing prey. Consequently, a tight-fitting lid or cover slide is absolutely mandatory for any aquarium housing a betta. Additionally, leaving a gap of at least one to two inches of air space between the water surface and the lid is recommended. This not only prevents escapes but also ensures they have access to warm, humid air above the water, which is vital for their labyrinth organ.

Reproduction

Oviparous

Betta splendens is a bubble nester, a reproduction strategy where the male builds a nest of air bubbles bound by mucus at the water's surface. Spawning involves an elaborate courtship display and a physical embrace under the nest where the male fertilizes the eggs and places them individually into the bubbles. After spawning, the female must be immediately removed as the male becomes highly aggressive while guarding the nest. The male takes sole responsibility for protecting the eggs and newly hatched fry until they become free-swimming, at which point he must also be removed to prevent cannibalism.

Compatibility & tankmates

Solitary

Due to their extreme territoriality, male Koi Galaxy bettas cannot be housed with other bettas, nor should they be kept with fish that look similar, have long fins, or exhibit bright colors that might trigger aggression. Suitable tank mates in larger setups include peaceful, short-finned bottom dwellers like Corydoras catfish, Kuhli loaches, or small, non-nipping schooling fish like Harlequin Rasboras. Additionally, larger invertebrates such as Nerite snails or Amano shrimp make excellent companions because they do not provoke the betta. Aggressive, fast-moving, or fin-nipping fish like Tiger Barbs must be strictly avoided.

Tank level

Top/Middle

The Betta splendens var. Koi primarily occupies the middle and top levels of the aquarium. As labyrinth breathers, they possess a specialized organ that allows them to breathe atmospheric air directly from the water surface, requiring frequent trips to the top. To support this behavior, they prefer resting spots near the surface, such as the leaves of tall plants or floating betta hammocks. Ensuring a clear space at the surface and minimal surface agitation is important for their breathing comfort.