Betta smaragdina Care Guide - Emerald Betta Setup, Diet & Breeding

Betta smaragdina, commonly known as the Emerald Betta, is a small labyrinth fish celebrated for its iridescent green to turquoise body. Depending on the population and mood, the scales can show blue, steel and emerald tones, while the fins may display red, green or blue edging and attractive barring.

Males are typically the more brightly coloured sex and develop longer, fuller fins. Like other members of the Betta splendens complex, this species can flare its gill covers and spread its fins during courtship, displays of dominance and encounters with rivals.

In nature, Emerald Bettas occupy quiet, densely vegetated waters with little current. Their labyrinth organ allows them to breathe atmospheric air, an adaptation that helps them survive in warm habitats where dissolved oxygen may fluctuate.

This is a territorial and intelligent fish rather than a conventional schooling species. Wild Betta smaragdina populations are valued by aquarists for their natural colours, courtship behaviour and close connection to the wild forms that contributed to the development of domesticated splendens-complex bettas.

Betta smaragdina is native to northeastern Thailand and adjoining parts of Laos in mainland Southeast Asia. It inhabits slow-moving and shallow freshwater environments, including marshes, flooded fields, ponds and small streams.

A single Emerald Betta should be provided with at least 20 litres, although 30 litres or more is preferable for a stable community setup. A tank measuring roughly 45 × 25 × 25 cm or larger gives useful floor space, while a secure lid is important because bettas can jump and need access to warm air above the water. Use gentle filtration and subdued flow, with dense planting, floating plants, roots, leaf litter and other sheltered areas. A dark, fine-grained substrate helps display the fish's colours and supports rooted plants; avoid sharp decor that could damage the fins.

Males reach approximately 6 cm (2.4 in) in total length, while females are usually smaller at around 5 cm (2.0 in).

Betta smaragdina is primarily a carnivorous micro-predator. Offer a varied diet of high-quality betta or small carnivore pellets supplemented with frozen or live foods such as brine shrimp, daphnia, mosquito larvae, bloodworm and finely sized insect-based foods. Small portions fed regularly are preferable to heavy meals, and uneaten food should be removed promptly.

A single Betta smaragdina can share a peaceful, well-planted aquarium with small rasboras, peaceful tetras, unobtrusive small corydoras and calm kuhli loaches, provided the aquarium offers sufficient space and cover. Avoid fin-nipping species, boisterous fish and other territorial anabantoids. Males should not be housed together, and keeping males and females together permanently can result in aggression unless the aquarium is spacious and carefully managed. Shrimp may be treated as prey, while very small snails can be harassed.

Betta smaragdina is a bubble-nesting species. Condition a compatible male and female with nutritious live or frozen foods, then introduce them to a gently filtered breeding aquarium with floating cover and calm, shallow water. The male builds a bubble nest and embraces the female to release the eggs, which he collects and places in the nest. Remove the female after spawning if she is being harassed, and separate the male once the fry become free-swimming. The eggs usually hatch in around 24 to 48 hours.

Males are generally larger and more intensely coloured, with longer, more elaborate fins and stronger iridescent green or blue markings. Females are usually shorter-bodied, less vividly coloured and have smaller, more rounded fins; mature females may show a visible ovipositor spot.