Betta Smaragdina Overview and Care Guide

The world of Bettas is expanding with the popularity of this unique species. Even though we may only see the one type of Betta sold at retailers, the elegant Betta smaragdina can make a great pet, too.  

In this post, we will cover some important information in Betta smaragdina care that will help guide you along the path to success of this colorful aquatic pet. 

Quick Facts:

  • Size: Males 1.97 to 2.37 inches. Females 1.97 inches or smaller
  • Colors: Males have a red body with iridescent scale tips which present as blue or emerald green. Females have a brown body with two black stripes. 
  • Lifespan: 3 to 4 years
  • Origins: Eastern Thailand and Malaysia
  • Level of Expertise: Moderate
Betta Smaragdina

What is the Betta Smaragdina?

The Betta smaragdina is closely related to the Betta splendens (the common species sold in small cups at pet retailers). It is also known by other names in the industry including the Mekong Fighting Fish (from its habitat of origins), Emerald Green Betta, and the Blue Betta. 

Betta smaragdina is considered a cryptic species, meaning they look similar to other Betta species, but they possess different genetics. Interestingly, there are 72 distinct fish that we would lump together under the title of “Betta”. B. smaragdina is one group of fish found in the bubble-nesting family of the Betta genus. 

B. smaragdina originated in eastern Thailand in the slow-moving waters of ponds, streams, rice paddies, or even in ditches on the side of the road. Betta smaragdina (like all Bettas) possess a small organ (the labyrinth) that allows them to breathe oxygen from the atmosphere, so their watery world does not have to be perfect for their survival. 

The Appearance of the Betta Smaragdina

Betta smaragdina is smaller than others, measuring in at 1.97 to 2.37 inches for males and 1.97 inches (or less) for females. In their natural habitat, B. smaragdina has shorter fins. However, due to captive breeding, the species is now displaying large plumed fins.

Perhaps the most striking feature of this species of Betta is its red body with tipped iridescent scales that show off a beautiful hue of blue or green. Since the iridescence is less pronounced on the bottom and top of the fins, this Betta appears to have stripes running along its body. The fins are also striped which makes it visually stunning. 

Females of B. smaragdina are noticeably smaller in body and fin size and are brown with two black stripes along the side of the fish. 

Both males and females of this Betta species have upturned jaws; however, males will also display blue or green iridescent on the operculum (gill plate). 

Temperament of the Betta Smaragdina

B. smaragdina were bred for fighting each other, and therefore should not be kept in same-sex tanks. However, in the right community and habitat, Betta smaragdina is a cheerful fish and can cohabitate quite nicely with a female of its species, small tetras, or corydoras. 

Betta Smaragdina Care

In an optimal tank habitat, your B. smaragdina could live up to four years. To help you achieve the long life of your Betta, here are some helpful tips on what your B. smaragdina needs. 

Tank Size

The size of the tank you have will determine the lifestyle of your Betta smaragdina. A single male should have at least 5 gallons of water to live out his life. Bowls, cups, and other “fancy” containers, that may be visually pleasing to us, are not always a suitable home for a Betta and most often prove to be more of a hassle to maintain, than a larger, more suitable aquarium. 

For the Betta smaragdina, aim for at least 10 gallons of water and increase the size (up to 30 plus gallons) if you want to keep a breeding pair or other community fish with your B. smaragdina. 

We also recommend having a lid in place. This will not only help maintain the proper heat and light, but B. smaragdina is also quite athletic and has been known to leap out of the aquarium. 

Water Quality

This species of Betta is very hardy and can live in a wide range of water conditions. However, we should aim for optimal. B. smaragdina prefers a warmer tank ranging from 70 to 80 degrees Fahrenheit. This is best achieved using an aquarium heater. 

Do not place your tank in direct sunlight as this creates spikes and drops in the water temperature. 

This species of Betta thrives in a mid-range pH (6 – 7.5). If your tank is too acidic, then increase your water changes, add natural plants, or use pH reducing (or enhancing) chemicals to achieve the optimal zone. 


When setting up your B. smaragdina’s habitat, know that they prefer densely populated aquarium plants and decorations (which they will use as territory markers and places to hide and destress).

The best and most readily aquarium plants for your Betta include;

  • Java Fern: This plant is low-maintenance and displays long thick green leaves. It is a slow grower and has a root system that will help establish it in your tank. It is also available in different varieties, but with the same ease of care. 
  • Cryptocoryne: Easy to care for and doesn’t mind a low-light environment, the “crypt” plant comes in a variety of colors (bronze, green, red, and tropica) with broad, wavy leaves. 
  • Marimo Moss Balls: These unique plants are actually “rolled” algae and can be tossed into your aquarium for your Betta to nibble on or move around at will. They don’t mind low light and are relatively inexpensive and easy to maintain.
  • Anubias: This plant has beautiful green leaves and long-rooted stems that can be placed in aquarium decorations or lightly pushed into the substrate. It is available in different shapes and sizes to add variety for your Betta.
  • Water Sprite: This plant can be used as a floater or fix it into your substrate or an ornament. It’s great at absorbing tank toxins, grows quickly, and is perfect for Bettas to build a bubble nest in.


When it comes to setting up an aquarium, many folks are happy to go with aquarium gravel. This is readily available, easy to maintain, and a fine choice for Bettas. However, to better duplicate their natural habitat, we highly recommend using sand or leaf litter. 

When choosing either of these options, be sure to only use store-bought. Sand and leaves taken from outdoors may contain pesticides and other toxins that could be fatal to your aquarium pets.

Indian almond leaves are the best choice for B.smaragdina. Your Betta will love to nibble on them and they also provide natural tannins as they decay which are beneficial to the health of your fish. 


Even though your Betta smaragdina does enjoy eating the odd plant here and there, this species is mainly a carnivore. In the wild, B. smaragdina will eat insects and larvae from the surface of the water and those that sink, as well as small crustaceans like snails

Feed your Betta once or twice a day using a diet of frozen or live foods such as artemia, bloodworms, and daphnia

Pellet and flake foods will do in a pinch but are not recommended for the long term.

General Maintenance

When setting up a ten-gallon (or more) Betta smaragdina aquarium you will want to use a low-flow aquarium filter (Bettas like slow-moving water). If you cannot turn down the flow of your filter, use a smaller one or create a low-flow area using aquarium decorations.

B. smaragdina also prefers low light, so again, use less wattage in your aquarium bulb or create shaded areas using floating plants. You will also want to provide your Betta with a natural 12-hour day/night cycle. 

We recommend a weekly 10 percent water change of your Betta smaragdina habitat. This can be performed using an aquarium vacuum in the gravel or by gently turning the leaf litter to release the waste, then siphoning out the debris with the water. 

When replacing the water, always use a dechlorinating product to remove the chlorine and chloride found in many region’s tap water. 

Final Thoughts

If you love the Betta species or just want to try your hand at a different type of Fighting Fish, then the B. smaragdina may be right for you. Follow our guidelines for proper setup of the aquarium, feeding, and maintenance of the Betta smaragdina, so you can enjoy the beauty and uniqueness this aquatic pet brings to any home or office for years to come.