Krabi Mouthbrooding Betta (Betta simplex) — 3,5cm

Overview

The Krabi Mouthbrooding Betta (Betta simplex) is a rare, critically endangered mouthbrooding betta from Thailand that rewards experienced keepers with fascinating behavior and striking natural beauty. Endemic to Krabi Province in southern Thailand, where it inhabits karst springs, wetlands, and vegetated margins of slow waters, this species reaches 4 cm in length and is prized for its subtle but refined coloration and unique paternal mouthbrooding reproductive strategy. Unlike bubble-nesting Bettas, the male B. simplex incubates eggs and fry in his mouth for extended periods, displaying remarkable parental dedication. As a critically endangered species often wild-collected, captive-bred stock is strongly preferred for conservation reasons. Available for sale UK from specialist suppliers, this species is ideal for experienced Betta enthusiasts seeking a rare, challenging, and biologically significant wild Betta species.

Appearance and Physical Characteristics

Betta simplex exhibits a slender, streamlined body shape with a slightly compressed profile. Males display a base coloration of olive-brown to greenish-brown with subtle iridescent blue-green or turquoise highlights on the scales and fins. The unpaired fins are moderately elongated and show delicate patterning with blue, green, and red highlights. Females are plainer, with shorter fins and more subdued coloration. Males are typically more colorful and display more pronounced finnage during breeding. Both sexes have large, expressive eyes and a slightly upturned mouth. Coloration is subtle and refined rather than vibrant, rewarding close observation under subdued lighting.

Natural Habitat and Distribution

Betta simplex is endemic to Krabi Province, southern Thailand, where it inhabits karst springs, wetlands, and vegetated margins of slow waters. These habitats are characterized by clear to slightly turbid, soft to moderately hard water with neutral to slightly acidic chemistry (pH 6.0-7.5). Water temperatures are warm (24-28°C). Dense vegetation provides cover and foraging areas. This species is critically endangered in the wild due to habitat loss and over-collection, making conservation and captive breeding efforts essential.

Aquarium Setup and Environment

A minimum aquarium capacity of 60 liters is recommended for a pair of Krabi Mouthbrooding Bettas. The tank should be heavily planted with dense vegetation, floating plants, and hiding spots. A dark substrate enhances coloration. Include driftwood, dried leaves, and caves. Filtration should be very gentle—sponge filters are ideal. Lighting should be subdued. A tight-fitting lid is absolutely essential.

Water Parameters and Quality

Krabi Mouthbrooding Bettas require soft to moderately hard water with neutral to slightly acidic chemistry. Maintain temperatures between 24-28°C, with 26°C ideal. The pH should range from 6.0-7.5. Water hardness should be soft to moderately hard. Maintain zero ammonia and nitrite, and keep nitrates below 20 ppm through regular water changes. Excellent water quality is essential.

Feeding and Nutrition

Betta simplex is a carnivore. Offer a varied diet of high-quality small carnivore foods such as live or frozen bloodworms, daphnia, brine shrimp, mosquito larvae, and quality micro pellets. Occasional small insect-based foods are beneficial. Feed once daily in small portions, and fast one day per week. Variety ensures complete nutrition.

Behaviour and Temperament

Betta simplex is classified as semi-aggressive but is generally calm. Males are territorial toward other males. These fish are most active during dawn and dusk, becoming bolder in dimly lit aquariums with plenty of cover. Males display to females with spread fins and intensified coloration. Like all Bettas, they can breathe atmospheric air.

Tank Mates and Compatibility

Best kept singly or as a carefully managed pair/species setup. If tankmates are used, choose very peaceful, non-nippy species in a larger planted tank. Snails may be acceptable. Avoid large or boisterous fish, fin-nipping species, other aggressive bettas or territorial anabantoids, fast-feeding community fish that may stress it, and large predatory fish.

Breeding

Betta simplex is a paternal mouthbrooder. The male incubates the eggs and fry in his mouth. Breeding usually requires a calm, well-structured pair setup with soft, clean water, dense cover, and minimal disturbance. After spawning, the male collects eggs in his mouth and incubates them for 10-18 days, during which time he does not feed. Remove the female after spawning. After release, fry can accept newly hatched brine shrimp and microworms. Provide frequent small feedings and pristine water quality.

Why Buy from Tropical Fish Co

Tropical Fish Co is the UK's specialist source for rare wild Betta species, including captive-bred Krabi Mouthbrooding Bettas. Every fish is quarantined, conditioned, and health-checked. We support conservation breeding and ethical sourcing. We offer a live arrival guarantee, secure packaging, and next-day delivery. Order today and support conservation of this critically endangered species.