Betta simplex Breeding Guide

Breeding the Krabi mouthbrooder Betta simplex: a paternal mouthbrooding wild betta from Thai limestone springs where the male incubates eggs orally for 9-16 days.

Overview

Betta simplex, the Krabi mouthbrooder (family Osphronemidae), is a wild betta endemic to Krabi province in southern Thailand, with populations near Ao Luek associated with limestone springs. Seriously Fish gives a maximum standard length of 45-60 mm. It is a paternal mouthbrooder, in which the male incubates the eggs orally.

Sexing

Seriously Fish notes males are larger and display a greater extent of iridescent scaling on the head, a broader head shape and more extended fins than females.

Conditioning

Condition adults on small live and frozen foods. Seriously Fish lists 20-28 C, pH 7.0-8.0 and 54-215 ppm hardness, reflecting the hard, alkaline limestone-spring water of its origin; a single pair or a small group can be used for breeding.

Breeding Setup

A quiet, well-covered tank with hard, alkaline water and some cover suits the species. As a mouthbrooder, no bubble nest is built, so structure is for security rather than spawning substrate.

Spawning Behaviour & Trigger

Seriously Fish describes courtship leading to an embrace in which eggs and milt are released, with the male wrapped around the female. Fertilised eggs are caught on the male's anal fin, then the female picks them up and spits them into the water for the male to retrieve and hold orally, repeating until the female is spent of eggs.

Egg & Fry Care

Seriously Fish gives an incubation period of 9-16 days, after which the male releases free-swimming fry. Reports suggest the adults do not harm the young, which may develop faster when left with the parents. Fry are large enough to accept motile foods such as microworm and Artemia nauplii immediately, though excessive brine shrimp may cause problems; use small, regular water changes rather than large ones.

Common Challenges

Holding males may spit a brood prematurely if stressed or disturbed, so the tank should be kept quiet and stable. Hard, alkaline water and a calm environment give the best brooding success.