Betta Macrostoma

Looks how to spot one

scales

A chunky, large-mouthed fish with a robust body. Males are brilliantly coloured with a bright orange body, two black horizontal bars on the flanks, an orange cheek bearing a large black blotch, and a dorsal fin adorned with a striking black-and-orange eye-spot. The caudal fin shows curved black bars with orange patches, and all fins have dusky edges. Females are much plainer, usually brown with faint horizontal bars and at most a hint of orange.32

Personality what they are like

Relatively peaceful but easily stressed. They can be kept in pairs or small groups in a large species-only tank, but they may eat very small tankmates. They are sensitive to sudden movements and can crash into glass when frightened, sometimes fatally.32

Daily activity how busy a day looks

Active swimmers that need plenty of open space. A minimum of 20 gallons for a pair, and 50 gallons or more for a small group. Dim lighting and plenty of cover (driftwood, caves, plants) help reduce stress.25

Grooming and care the hands-on bits

Regular maintenance is essential: perform 20-25% water changes weekly or twice weekly. They are sensitive to nitrates and ammonia, so good filtration and live plants are recommended. Avoid strong lighting and direct sunlight.32

Home where they are happiest

Water temperature 24-26°C (75-79°F), pH 6.0-7.5, hardness 1-10 dKH. The tank should mimic a slow-moving, shallow stream with a gravel bottom, driftwood, caves, and plenty of plants. A species-only tank is strongly advised. Note: This species is protected by law in Brunei; it is illegal to catch or possess wild specimens. Only captive-bred fish should be kept.236

Food basics what goes in the bowl

Omnivorous with a high-protein requirement. They rarely accept dry foods; offer live or frozen foods such as brine shrimp, daphnia, glassworms, bloodworms, mosquito larvae, and white worms.32

Company who they like around

Best kept in a species-only tank. Pairs can be housed in a 20-gallon tank; groups need at least 50 gallons. They are paternal mouthbrooders: the male incubates the eggs in his mouth for 21-35 days. Do not keep with other fish species, as they may eat small tankmates or be stressed by larger ones.325

The story where it all began

Betta macrostoma was first described by C. T. Regan in 1910 from a specimen collected in Sarawak, Borneo. It is one of the rarest wild bettas in the hobby. Agricultural development has destroyed much of its natural habitat, leading to a steep population decline. In Brunei it was once thought extinct, but was rediscovered in the 1980s. Today it is listed as Vulnerable on the IUCN Red List and is legally protected in Brunei, where capturing wild fish is prohibited. Most specimens in the aquarium trade are captive-bred, which helps reduce pressure on wild populations.726

Recognised by the official bits

IUCN Red List

Vulnerable (D2)6