Brunei Beauty
Betta macrostoma
The 'Big Mouth Betta' or 'Brunei Beauty' (10 cm). Legendary fish, large and very rare fire red/orange labyrinth fish with black bands and spotted mask (in the male). Considered the Holy Grail of wild Bettas, demands meticulous care, covered tanks and kingly maintenance costs.
Température de l’eau
22 - 26 °C
Valeur du pH
6 - 7
Type d'eau
Eau douce
Niveau dans le bac
Fond et milieu
Taille adulte
11 cm
Volume minimal du bac
>= 100 L
Groupe minimal
>= 1
GH
1 - 10 dGH
KH
1 - 5 dKH
TDS
25 - 200 ppm
Conductivité
39 - 313 uS/cm
Description de l'espèce
Geographical Origin and Habitat: Endemic to Brunei (north-western Borneo). Inhabits pools and slow clear water flows in forest streams. Usually found under waterfalls where the water is highly oxygenated and surprisingly cool for the area.
Taxonomy and Morphology: Brunei Beauty (Betta macrostoma). The "Holy Grail" of wild Betta lovers. It is one of the largest Bettas; "macrostoma" means large mouth, necessary for oral incubation. Massive body, large scales and straight dorsal profile.
Social Behavior: Extremely aggressive towards conspecifics. Can only be kept singly or in a bonded pair. Even females can be brutal with each other or with the male. A continuous visual escape route must be provided in the tank.
Coloration and Sexual Dimorphism: The male has an inimitable livery: coal-black head (in breeding dress), bright rust-red flanks and a dorsal fin decorated with a showy ocellus (black spot) bordered in red and white. Brown females with two blackish longitudinal stripes.
Soins, reproduction et cohabitation
Aquarium Setup: Dedicated 80-100 cm (32-40 inches) tank. Clear water, smooth rocks and woods. FUNDAMENTAL an absolutely hermetic cover (they jump through millimetric cracks) and strong aeration with moving water, unlike swamp Bettas.
Diet and Feeding: Large carnivorous predator. In nature it eats insects, small fish and amphibians. In the aquarium it requires an abundant mix of live and frozen food (bloodworms, mysis, chopped earthworms). Prone to obesity if overfed with industrial pellets.
Water Quality: Requires very clean and cooler waters than the typical Betta (22-26°C / 71-79°F). Temperatures constantly above 27°C (81°F) weaken the immune system leading them to death by parasitosis in a few months. Nitrates close to zero.
Compatibility and Cohabitation: To be strictly kept in a tank dedicated to the single pair. Their size and aggressiveness make them a danger to small fish, and they get fatally stressed in the presence of territorial Cichlids or fast fish.
Aquarium Breeding: Mouthbrooder. Difficult to achieve. Mating is very violent. The male holds the eggs for 18-35 days! Any minimum disturbance (a finger on the glass, a water change) will lead him to instantly devour the eggs.
Risks and Diseases: Very expensive and delicate. Suffers dramatically from drops in water quality and summer temperature peaks. Protected species by the Sultan of Brunei, export of wild specimens is illegal; legal specimens come from captive breeding.
Origine et répartition géographiques
Endemic to Brunei (north-western Borneo). Inhabits pools and slow clear water flows in forest streams. Usually found under waterfalls where the water is highly oxygenated and surprisingly cool for the area.
Origine
Amérique centrale et CaraïbesAsie du Sud et du Sud-Est
Profil de poisson
- Tempérament
- 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.
- Régime alimentaire
- 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.
- Espérance de vie
- 3-5 years
- Taille adulte
- 11 cm
- Ratio des sexes
- 1:1 ratio
- 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.
- Fréquence d'alimentation
- 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.
- Charge biologique
- 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.
- Courant
- 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.
- Risque de saut
- 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.
- Compatibilité et compagnons
- Species only
- 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.
- Niveau dans le bac
- 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.
Modèles et paramètres scientifiques
FishBase
Fenêtre sur les données scientifiques officielles de l’espèce
FishBase v25.04Données synchronisées le : 15/06/2026
- Niveau trophique
- 3,3 ± 0,4 se
- Résilience
- Élevée (moins de 15 mois)
- Singularité phylogénétique (PD50)
- 0.5
- Relation bayésienne longueur-poids
- a = 0.01, b = 2.97
- VulnérabilitéVulnérabilité faible (10 / 100)
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