Furry Diary

Not furry, but we like them anyway.

Emerald Betta

Betta smaragdina Ladiges, 1972

Also called Blue betta, Mekong fighting fish, Emerald green betta

SpeciesShort profile

From Mekong and Chao Phraya river basins of Thailand and Laos, especially the Khorat Plateau (Isan) of north-eastern Thailand.123

At a glance the quick version

Length6 to 7 cm213
Sizesmall

Seriously Fish gives 60 mm standard length; FishBase gives 7 cm total length.

Shimmering emerald and blue colour
Hardy air-breathing fish
Natural colour forms such as the Guitar variety
13

Looks how to spot one

Scales, slender labyrinth fish

A short-finned wild betta with a sturdy build. Its emerald and blue shine comes from tiny light-reflecting crystals in the skin. It breathes air at the surface using a labyrinth organ.13

ColoursReddish-brown bodyIridescent green or blue scale spots (males)Blue fins with red rays (males)Brown with two darker stripes (females)13

Personality what they are like

Males are territorial with one another, but with lots of cover several can live together. Females are calmer.2

Daily activity how busy a day looks

Calm swimmer that prefers still or slow water with plants.23

Grooming and care the hands-on bits

Use a tight lid and keep warm, humid air above the water surface. Keep water clean with gentle filtration.21

Home where they are happiest

A tank of roughly 40 litres (45 x 30 cm base) for a pair. Temperature 22-28 C (FishBase gives 24-27 C), pH 5.5-7.5 (FishBase gives 6.0-8.0), soft to moderately hard water. Dense plants, floating cover and leaf litter suit it.21

Food basics what goes in the bowl

Small invertebrates in the wild. In the aquarium it takes dried food plus regular live or frozen daphnia, brine shrimp or bloodworm.23

Company who they like around

Best kept alone or as a pair, or in a species tank with plenty of hiding places; not a typical community fish.2

The story where it all began

Described by Ladiges in 1972 from Nong Khai in north-eastern Thailand. In Thailand it has been line-bred for generations, and it is also selectively bred for the ornamental trade, giving several colour forms.123

Fun facts for the dinner table

  1. 1

    Its green and blue glow is structural colour, made by hexagonal crystals smaller than half a micrometre that bend and reflect light.3

  2. 2

    A natural colour form called Guitar, with distinctive fin markings, comes from north-eastern Thailand.3

  3. 3

    Its Thai name translates roughly as green fighting fish.3

  4. 4

    The male builds a bubble nest and guards the eggs and fry.2

Recognised by the official bits

IUCN Red List
Data Deficient (assessed 19 January 2011)1
Taxonomy
Family Osphronemidae; described by Ladiges in 1972; type locality Nong Khai, Thailand2

The care rhythm Furry Diary remembers it for you

A typical home-care rhythm for a Emerald Betta. It is our own starting plan, not a vet's advice, and you can change every line in the app.

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Where this comes from

Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.

  1. FishBase: Betta smaragdina summary fishbase.seused for origin, size, water parameters, IUCN status, colours
  2. Seriously Fish: Betta smaragdina seriouslyfish.comused for care, tank size, diet, behaviour, type locality
  3. Wikipedia: Betta smaragdina en.wikipedia.orgused for other names, colour science, varieties

Checked 2026-09-30. Text is written in our own words from these sources.