Betta siamorientalis

Overview

Betta siamorientalis is a small bubble-nesting fish from eastern Thailand and neighboring areas. Formerly treated as a dark form of Betta imbellis, it was subsequently recognized as distinct. A dark brown or black body and two usually reddish bars on the black gill cover are useful clues.

Distribution & habitat

Records include Chachoengsao, Sa Kaeo, Prachin Buri, and Chon Buri in Thailand, Banteay Meanchey in western Cambodia, and an unspecified Vietnamese locality. It occupies still or slow water in marshes, flooded fields, rice paddies, and densely vegetated pond or channel margins, using plants for shelter and nesting.

Aquarium setup

A pair needs a footprint of about 45 × 30 cm. Dense planting, subdued light, and surface cover are valuable. Wood, roots, pots, and pipes provide separate retreats. Dried leaves add cover and support microorganisms useful to fry; natural peat is unnecessary.

Use gentle circulation, for example an air-driven sponge filter. A secure cover prevents jumping, while an unfilled space above the water retains humid air for breathing.

Diet & feeding

Small insects and other invertebrates are probable natural foods. Captive fish usually learn to accept dry preparations, supplemented regularly with small live or frozen Daphnia, brine shrimp, and bloodworms. Newly hatched crickets or fruit flies are options after being fed fish food or plant matter. Avoid excessive portions and obesity.

Behaviour & compatibility

A busy general community is unsuitable. Maintain it alone or with exceptionally peaceful companions; larger, vigorous fish can intimidate it and compete for food. Multiple males may coexist when cover breaks sightlines extensively, but this is conditional rather than guaranteed. Separate pairs are preferable for breeding.

Sexual dimorphism

Males are brighter and longer-finned. Females pale and develop dark flank bars near spawning.

Breeding

The male constructs a bubble nest in a container, beneath a broad leaf, or among fine surface plants, usually excluding the female until completion. A tight cover maintains the warm humid air required by developing fry.

Spawning embraces occur below the nest. The male installs eggs while the female helps recover fallen ones. He then assumes nest care; adults can usually remain. Eggs hatch after about 24–48 hours, and larvae stay another three to four days while absorbing yolk. The male retrieves falling young and may relocate a threatened nest.

Care declines after free swimming, and adults generally leave offspring uneaten. Begin with microscopic foods such as Paramecium, then introduce microworms and brine shrimp nauplii. Provide small varied meals two or three times daily and regular modest water changes.

Notes

Gill-cover bars vary between populations and may be pale red, greenish-silver, silver, or inconspicuous. Red bars alone do not establish Betta splendens identity. Check the red crescent and thin black tail margin together with the absence of dark transverse tail bars.