Species description

Care, breeding and tankmates

Fish profile

Temperament

Semi-aggressive

Betta macrostoma is a shy but territorial species that exhibits moderate aggression, particularly towards conspecifics. Males will defend their territory vigorously, and females can also be assertive. Despite their size, they are easily startled by sudden movements or loud noises outside the tank.

Diet

Omnivore

They are strict carnivores requiring a high-protein diet consisting of live or frozen foods. Preferred foods include brine shrimp, daphnia, bloodworms, glassworms, krill, and Mysis shrimp. They rarely accept commercial dry flakes or pellets, and overfeeding must be avoided as they are prone to obesity and internal infections.

Life expectancy

3-5 years

Under optimal care and stable water parameters, Betta macrostoma typically lives between 3 and 5 years in captivity. Achieving their maximum lifespan requires maintaining pristine water quality, a high-quality carnivorous diet, and minimizing stress. They are highly susceptible to disease if kept in suboptimal water conditions.

Sex ratio

ONE_TO_ONE

It is highly recommended to keep Betta macrostoma in bonded pairs (1:1 ratio) or individually. Keeping multiple males or mismatched groups in small aquariums can lead to severe territorial aggression and injury. If kept in a group, a very large tank with numerous physical barriers and hiding spots is mandatory.

Feeding frequency

Twice daily

It is recommended to feed Betta macrostoma once or twice a day in small portions that they can consume within a few minutes. Fasting them for one day a week can help maintain healthy digestion and prevent obesity. During mouthbrooding, the male will not feed for several weeks and should not be offered food.

Bioload

Medium

Betta macrostoma has a medium bioload due to its relatively large size (up to 10-12 cm) and high-protein carnivorous diet. They produce a moderate amount of waste, which requires efficient but gentle filtration to avoid stress. Frequent water changes are necessary because they are highly sensitive to nitrates and bacterial proliferation in the water column.

Flow

Stagnant

This species prefers weak to gentle water flow, mimicking the slow-moving forest streams and pools of their natural habitat in Borneo. Strong currents will cause them stress and exhaust them, potentially leading to illness. Air-powered sponge filters or gentle canister filters with spray bars are ideal filtration choices.

Jump risk

Yes

This species is an exceptional and powerful jumper that can escape the aquarium through even the smallest openings. A tightly fitting lid is absolutely mandatory, and any gaps around cables or tubing must be carefully sealed. Keepers often leave a generous gap between the water surface and the lid to prevent them from injuring themselves during jumps.

Reproduction

Oviparous

Betta macrostoma is a paternal mouthbrooder, which makes their breeding behavior unique and highly fascinating but challenging. The female initiates spawning, and after fertilizing the eggs, the male carries them in his mouth for 14 to 21 days. The male is highly sensitive during this period and may swallow the brood if stressed by noise, tankmates, or poor water quality.

Compatibility & tankmates

They are best kept in a species-only aquarium due to their territorial nature, sensitivity to water quality, and specific environmental needs. Smaller tankmates will be viewed as prey, while fast, boisterous tankmates can easily intimidate them. Keeping them as a bonded pair is the safest and most rewarding setup.

Tank level

Middle/Bottom

Betta macrostoma primarily occupies the bottom-to-middle levels of the aquarium, where they spend time hiding among leaf litter, roots, and caves. They will periodically swim to the surface to breathe atmospheric air using their labyrinth organ and to feed. Providing low-light areas and overhangs in these zones helps them feel secure.