Named after their sickle-shaped caudal (tail) fin, which gives them a unique and distinctive appearance.
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Named after their sickle-shaped caudal (tail) fin, which gives them a unique and distinctive appearance.
Betta falx has an elongated body with earthy brown tones, highlighted by subtle iridescence under proper lighting. The signature “sickle” shape of the tail fin is where it gets its common name. Fins have delicate transparent edges and a streamlined appearance compared to the ornate Betta splendens.
2-3 years
Carnivorous; prefers high-quality Betta pellets or flakes, supplemented with occasional live or frozen foods.
Betta falx is a wonderful choice for aquarists looking for a wild betta with unique breeding behavior and a more peaceful nature than the popular Siamese fighting fish. They bring a sense of natural elegance to planted aquariums and reward keepers with fascinating courtship and parental care displays.
Intermediate
10 gallons
5.5 – 7.0
Soft to moderately hard
24°C – 28°C (75°F – 82°F)
2.5 inches
Peaceful small fish like rasboras, small tetras, Corydoras, and other calm betta species
Betta falx
Osphronemidae
Sumatra, Indonesia
Semi-aggressive; territorial males but peaceful toward non-threatening species
Betta falx thrives on a diet of meaty live or frozen foods. While they can adapt to high-quality pellets, their health and coloration improve significantly with varied protein-rich foods. Offer live daphnia, mosquito larvae, and bloodworms regularly, and rotate with pellets to ensure complete nutrition.
Mouthbrooder – male incubates eggs in his mouth until fry are released
Betta falx is a paternal mouthbrooder. The male holds fertilized eggs in his mouth for around 10–14 days, refraining from eating during this time. Once the fry are released, they are free-swimming and relatively large compared to other betta fry, making them easier to raise. Breeding is best done in a separate tank with dense plant cover and calm water.
They prefer stable, slightly acidic to neutral pH and warm, soft water. Avoid strong currents as they inhabit slow-moving streams in nature. Maintain ammonia and nitrite at 0, and keep nitrate under 20 ppm. Floating plants and dim lighting help mimic their natural habitat and reduce stress.
Sensitive to sudden parameter changes. Fin rot, bacterial infections, and parasitic infestations are possible if water quality is neglected. Males may become lethargic if stressed during brooding. Copper-based medications should be avoided.
Can be aggressive, especially towards other male Betta fish. Best kept alone or in a species-specific setup.
Betta falx is a calm but alert species. Males establish small territories, especially during breeding. They often explore the tank, darting between plants and structures, and can coexist with peaceful species if provided with enough hiding spaces. Unlike Betta splendens, they are less prone to fin nipping and can be kept in pairs or small groups under the right conditions.
Betta falx, or the Sickle Betta, is a wild species native to Sumatra, Indonesia, where it inhabits calm, shaded blackwater streams rich in leaf litter. Unlike the aggressive Betta splendens, Betta falx displays a more subdued personality, making it suitable for community aquariums with peaceful tank mates. They are paternal mouthbrooders, with males carrying eggs in their mouths until fry are ready to swim freely. Keeping them healthy requires stable, slightly acidic water, plenty of cover from plants and driftwood, and a protein-rich diet. Their subtle yet beautiful appearance, combined with their unique breeding habits, makes them a favorite among wild betta enthusiasts who appreciate natural behavior over flashy fins.