Betta simplex

Betta simplex is a paternal mouthbrooding betta endemic to the limestone cave and spring systems of Krabi Province, southern Thailand. Males develop attractive bluish-green iridescent colouration on the body and unpaired fins, and the species has a somewhat more robust build than many other wild bettas of similar size.

The Krabi habitat features clear, moderately soft water rather than the tannin-stained blackwater typical of many Betta species. In the aquarium, slightly acidic to neutral water with moderate softness suits them best. They are relatively adaptable and represent a good choice for hobbyists transitioning from the common betta to wild mouthbrooding species.

Pairs are best kept in a dedicated species tank with plenty of plant cover. The male broods eggs for 10–14 days. Because their natural habitat overlaps with limestone formations, they may tolerate slightly harder water than most wild bettas — a helpful quality for keepers without access to RO equipment.