Known as the 'Brunei Beauty', Betta macrostoma is a large, highly sought-after wild mouthbrooding Betta. They possess a massive mouth and are voracious predators. Native to highly acidic, soft blackwater streams in Borneo, they require cool, pristine water to thrive. They are extremely prone to jumping and require a tight-fitting lid.
Betta Macrostoma At a Glance
Betta Macrostoma Tank Requirements
Will Betta Macrostoma fit in your tank?
Care guides tell you what Betta Macrostoma needs, the next question is whether your tank can safely provide it. Test Betta Macrostoma against your tank size, maintenance needs, and the fish you already keep before you buy.
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Betta Macrostoma Water Parameters
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Betta Macrostoma Temperament & Compatibility
Betta Macrostoma Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Male
Features striking orange-red coloration and a massive dorsal fin with an 'eyespot' pattern. Males are highly territorial towards each other. Best kept singly or in a proven male-female pair.
Differs in 2 traits from base species
Also known as: Male Macrostoma, Male Brunei Beauty
Female
Displays drab brownish-grey coloration, often with two horizontal bands. While less colorful and slightly less aggressive than males, she is still a formidable predator. Typically kept in a pair with a single male.
Differs in 3 traits from base species
Also known as: Female Macrostoma
Betta Macrostoma Care Guide Summary
The Betta Macrostoma, scientifically known as Betta macrostoma, belongs to the Anabantoids family group. Adults reach a maximum size of approximately 11 cm and have a fusiform body shape with a moderate growth rate. Classified as semi-aggressive, this species primarily occupies the surface, mid-level, and bottom zones of the aquarium and produces a medium level of biological waste.
To thrive, the Betta Macrostoma requires a freshwater only aquarium with a minimum volume of 80 litres and a tank length of at least 60 cm. Water temperature should be maintained between 20°C and 25°C, with a pH range of 4–6 and a general hardness of 0–5 dGH. A low water flow is preferred.
Due to its specialist needs, the Betta Macrostoma is best suited for fishkeepers who can provide a carefully planned setup. This species is available in 2 varieties: Male and Female. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Betta Macrostoma Habitat Setup
When setting up an aquarium for the Betta Macrostoma, a low water flow best suits their natural preferences. Because this species occupies the surface, mid-level, and bottom zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline, open swimming space in the centre of the tank for free movement, and sufficient floor space with hiding spots among rocks, wood, or dense planting. Useful additions include driftwood, which can serve as both a hiding place and a dietary supplement, leaf litter or blackwater tannins to replicate their natural soft-water habitat, and floating plants to diffuse overhead light and create shaded areas. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
Betta Macrostoma Compatibility Notes
Classified as semi-aggressive, the Betta Macrostoma is adaptable and can be kept singly or in a small group, offering flexibility when planning a community tank. When choosing tankmates, any fish small enough to fit in its mouth will likely be eaten, ornamental shrimp are not safe companions, conspecific aggression can be intense, especially in smaller tanks, territorial behaviour may cause issues if hiding spots or floor space are limited, and boisterous or fast-moving tankmates may cause this species undue stress. Selecting tankmates that favour different water layers from the surface, mid-level, and bottom zones can help reduce competition and territorial overlap.
Betta Macrostoma Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Betta Macrostoma.
29 Gallon Standard
30 Gallon Breeder
36 Gallon Bowfront
40 Gallon Breeder
55 Gallon Standard
60 Gallon Breeder
Show 15 more tank sizes
Betta Macrostoma Feeding & Diet Considerations
The Betta Macrostoma is a predatory species that will readily consume small fish, so nano or bite-sized tankmates should be avoided and will hunt and eat ornamental shrimp, making it unsuitable for shrimp-focused setups.
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Frequently Asked Questions About Betta Macrostoma
How big does Betta Macrostoma get?
Betta Macrostoma (Betta macrostoma) typically reaches a maximum adult size of approximately 11 cm. They have a fusiform body shape and a moderate growth rate.
What tank size does Betta Macrostoma need?
A minimum aquarium volume of 80 litres and a tank length of at least 60 cm are recommended for Betta Macrostoma. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Betta Macrostoma need?
Betta Macrostoma thrives in freshwater only conditions with a temperature range of 20–25°C, a pH between 4 and 6, and a general hardness of 0–5 dGH. A low water flow is preferred.
Is Betta Macrostoma peaceful or aggressive?
Betta Macrostoma is classified as semi-aggressive with an aggression score of 6 out of 10. They can work in community setups but may clash with certain tankmates.
Can Betta Macrostoma live alone?
Yes, Betta Macrostoma can be kept singly or in a group. They are flexible and adapt well to both setups.
Is Betta Macrostoma safe with shrimp?
No. Betta Macrostoma is known to eat ornamental shrimp and is not recommended for shrimp tanks. Even larger shrimp species like Amano Shrimp may be at risk.
Does Betta Macrostoma have any special tank requirements?
Yes. Betta Macrostoma benefits from leaf litter/blackwater, driftwood (digestion/hiding), and plants - floating in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Betta Macrostoma need a lid on the tank?
Yes. Betta Macrostoma is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.
Plants That Suit Betta Macrostoma
These plants pair well with Betta Macrostoma based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Amazon Frogbit
Limnobium laevigatum
Asian Watergrass
Hygroryza aristata
Asian Watermoss
Salvinia cucullata
Carolina Mosquito Fern
Azolla caroliniana
Common Duckweed
Lemna minor
Crystalwort
Riccia fluitans
Fish Similar to Betta Macrostoma
Betta Smaragdina
Betta smaragdina
A beautiful wild-type Betta species native to the Khorat Plateau of Thailand, known for its striking iridescent emerald-green scales. Unlike the domestic Betta splendens, they are slightly more peaceful and closely resemble their natural wild form. They are excellent jumpers and require tight-fitting lids.
Chocolate Gourami
Sphaerichthys osphromenoides
A delicate, highly specialized labyrinth fish native to the peat swamp forests of Southeast Asia. Known for its rich chocolate-brown coloration and vertical cream bands. It is notorious for being sensitive to water quality fluctuations and requires extremely soft, acidic 'blackwater' to thrive and resist bacterial infections. Best kept in a heavily planted, mature species-only setup or with very peaceful, small nano fish.
Bearded Cory
Scleromystax barbatus
A large, striking, and somewhat atypical relative of standard Corydoras. Native to the highly oxygenated, cooler coastal streams of Brazil, they require sub-tropical temperatures and will stress or die in standard tropical tanks. They exhibit strong sexual dimorphism. Highly social, they must be kept on a soft sand substrate to protect their sensitive barbels.
Chili Rasbora
Boraras brigittae
A striking, deeply red nano fish native to the blackwater streams and peat swamps of southern Borneo. They are extremely peaceful and require a mature, densely planted aquarium with soft, acidic water. Due to their tiny size, they are completely safe with adult dwarf shrimp and are ideal for nano setups.
Betta Imbellis
Betta imbellis
Known as the 'Peaceful Betta', Betta imbellis is a wild species closely related to Betta splendens. Unlike their highly aggressive domestic cousins, they can often be kept in pairs or carefully managed groups. They are native to blackwater swamps and require calm, tannin-stained water with plenty of cover. They are exceptionally prone to jumping.
Freshwater Shark (Wallago)
Wallago attu
An apex predator native to South and Southeast Asia, infamous for its immense size, huge mouth, and voracious predatory nature. It will consume any tank mate that fits into its capacious mouth and is known to bite aggressively when handled. This species is utterly unsuitable for standard home aquariums and requires an enormous custom pond or public aquarium setup.