Halfmoon Betta Fish – Origin, Definition, And More!

icon author linh nguyen

By Linh Nguyen Updated on 02 Feb 2023

Do you want to add a vibrant burst of color and calm into your home? Halfmoon betta fish might be just the pet for you! These tropical fish are known for their beautiful full “half-moon” tails, which make them appear like a growing rainbow in an aquarium. While they have unique physical characteristics that capture our attention, they also require special care. If you’re thinking about welcoming a halfmoon betta fish into your home, it's important to know what kind of environment and feeding routine will help them thrive and keep them healthy throughout their long lifespan.

In this blog post, we will explore the background of halfmoon bettas, common traits (both in appearance and behavior), as well as sharing tips on how best to care for your very own finned friend so that you can ensure years of happy bliss together!

A halfmoon betta fish

A halfmoon betta fish

1. The origin and history of the Halfmoon betta fish

The Halfmoon Betta Fish is known for its vibrant colors and beautiful fins. They are active swimmers but do not require a large tank, making them perfect for small aquariums. These fish can easily adapt to most water conditions and temperatures, making them an easy choice for beginner aquarists. Halfmoon Bettas have long flowing tails that resemble a crescent moon, hence their name. The males generally have brighter colors and longer fins than the females. Due to their beauty, they are some of the most popular freshwater fish on the market today. With proper care, these fish can live up to 3 - 5 years in captivity.

It was bred originally by an American breeder named Peter Goettner in 1982 before being further developed and refined by Delaval and Masillamoni. After persistent refinement, Masillamoni's Halfmoon betta won first place at the IBC convention in Alabama. This feat gained attention from FAMA Magazine, which helped spread awareness about this type of fish throughout the world. 

In the late 1990s, Thai breeders requested European and American counterparts for Halfmoon breeding stock to help them assert their dominance in crossbreeding techniques. Over time, halfmoons have become a priority for breeders around the world, as they strive to create superior specimens. This has created a new standard of excellence in "betta shows" and helped redefine what defines a quality fish.  Consequently, Halfmoon bettas are now one of the most popular breeds of betta fish, with their unique traits and appearance captivating people all over the globe. 

The development history of halfmoon betta fish is long and complex – starting from its original breeding in 1982 by Peter Goettner and continuing with refinement through Delaval and Masillamoni, which ultimately led to recognition from FAMA Magazine and Thai breeders seeking Halfmoon breeding stock. The result has been an aesthetically pleasing variety that continues to be admired and sought after by fish enthusiasts around the world. 

To learn more about the history and origins of this fish, read the article: The True Story of the Halfmoon.

2. What Do Halfmoon Bettas Look Like?

Halfmoon bettas possess distinct genetic traits that set them apart from other varieties. In particular, their tails must be spread out in a full 180-degree arc and must have multiple branching rays to provide extra support. Additionally, all caudal fin rays need to be straight and stable with no crooks or curves. These features make Halfmoon bettas a unique breed among aquatic life.

The name "halfmoon" comes from their fins that are shaped like a crescent moon when fully extended. They come in many color combinations and patterns, making them one of the most beautiful aquarium fish in existence.

Halfmoons have an impressive lifespan of up to five years with proper care, and they can even be trained to recognize their owners! These unique creatures make for an excellent addition to any home aquarium. With their captivating colors and personalities, it's no wonder why these fish have become so popular with hobbyists all over the world.

A male halfmoon betta

A male halfmoon betta

2.1. Males

Male halfmoon bettas often display brightly colored bodies and fins compared to female halfmoon bettas. Males typically have larger, rounder caudal fins that form a perfect 180 degree angle when spread out. This is the telltale sign of a male halfmoon betta, and makes them stand out in the crowd regardless of their coloration. In addition to this iconic tail shape, males also tend to have colors which are more vivid than those found on females. 

2.2. Females

Female halfmoon bettas are generally smaller than their male counterparts, with less striking colors and fins which don't flare as wide as males. Their tails aren't as large or as round either, nor do they make a perfect 180 degree angle when flared. Female halfmoon bettas can still be elegant and eye-catching, however they tend to be less flashy than their male counterparts. 

Overall, it is possible to differentiate between male and female halfmoon bettas by observing the size of their fins and the coloration of their bodies. Males often display larger, more colorful fins while females are smaller with less vibrant colors. It is important to remember that this isn't a hard and fast rule; some males may have duller colors or slightly misshapen caudal fins, and some females may have large or brightly colored tails. It just takes some practice to become familiar with identifying gender in these beautiful fish!

A female halfmoon betta

A female halfmoon betta

3. Definition of a beautiful halfmoon

There are at least three genetic factors that make up the halfmoon trait: 

  1. The tail must be spread out 180 degrees. 
  2. Branching at least three times.
  3. All caudal rays must be straight.

Let us examine these requirements in more detail.

3.1. The tail must be spread out 180 degrees.

With Halfmoon, you must be able to draw an XY line along the tail edges. This is only possible if the edges are straight and spread 180 degrees.

Tail, dorsal and anal fins should be in harmony, in balance: An arc should be able to be drawn starting from the dorsal fin A, smoothly curving around the tail and finishing at the anal fin B without any breaks. Such fish are then considered as having good balance.

When evaluating two Halfmoons, if all else is equal, the one with the greater tail length to body length ratio is considered to be more aesthetically pleasing.

The tail must be spread out 180 degrees

3.2. Branching at least three times.

The caudal ray should split early and branch up to a minimum of tertiary level. The ideal number of times the tail rays branch is four, while two times is considered suboptimal.


3.3. Most Challenging Trait: A long, straight tail edge

A perfect trailing edge should form a sharp angle when it meets the caudal arc. It should be a perfect line.

It is reasonable to assume that genetic factors play a role in bettas' fin rays and spread angle, comprising of both dominant and recessive genes. The gene for branching fin rays is dominant, while the gene for straight caudal rays and the gene for 180 degree spread are recessive. However, even if bettas inherit all the necessary genetic traits, they may not be able to reach their full potential due to poor water quality or rearing techniques.

caudal rays be straight

4. Some beautiful halfmoon betta fish lines

The Halfmoon Betta fish is much more popular for ornamental purposes than as a fighting fish. Their unique beauty and vibrant colors have captivated people worldwide, making them one of the most popular varieties of betta today. Every time they show off their impressive hues, they make people marvel at their beauty.

4.1. Red dragon halfmoon betta fish

The bright red hue of the fish's tail spreads out like a beautiful, yet mysterious blood moon. This fish captivates all who lay eyes upon it.

Red dragon halfmoon

4.2. Halfmoon nemo betta fish

The combination of the splendor of Halfmoon fish and the mischievous cuteness of Nemo makes them an especially special species. Fans of Finding Nemo should not miss out on this unique opportunity to admire these beautiful creatures.

Halfmoon nemo

4.3. Black halfmoon betta fish - extremely rare

This fish line is extremely hard to come by due to the difficulty of creating a pure black coloration, despite modern breeding techniques. It is also believed that this type of fish brings fortune and luck to its owner, making it highly sought-after. Therefore, hunting for one has become an incredibly difficult task.

Black halfmoon betta fish

Betta HM is currently bred with many different lines in order to create diversity, such as Dumbo HM and Koi HM. This variety makes the price of these fish quite affordable, yet they remain popular due to their beautiful tail shapes and the vast array of colors that result from hybridization. Ultimately, Betta HM still holds a great aesthetic value for many people.

5. Nurturing and Caring

Not only Halfmoon Bettas, but any betta lineage follows the same principle when it comes to raising them. Here I will share some of my own experiences on how to properly care for a Halfmoon Betta so that its tail is not damaged.

  1. A wide tank is necessary for a Hm to be able to swim and spread its large fin. The typical tank size should be 15cm x 15cm x 20cm.
  2. The water level should be kept above 10 cm; I personally use 15 cm as my water level.
  3. Take the Indian almond leaf, squeeze it vigorously, and then place it in water. Alternatively, soak the leaves separately outside and then pour them into the aquarium's water, this will give it a tea-like color. Add a pinch of salt, with a 15x15x20 tank, I would recommend 1/2 teaspoon of granulated salt. Change the water every 2-3 days with new leaves.
  4. Feeding is done in two ways:
    • For people with limited time, feed a worm the size of a peanut in the morning and ensure that the fish has eaten all of it by 4 PM. 
    • For those who have more free time, divide the worm into two meals throughout the day. Do not feed your fish after 5 PM as this increases their risk of developing diseases or fungal infections.
  5. If your betta appears to be too heavy, consider implementing a fasting period of 3-4 days and reducing their food intake as part of a weight loss plan.
  6. In case you are busy and can't change the water every 2 3 days (sometimes only), then take out the Indian almond leaf, and put it into the tank water, maybe 1 week.
  7. Let the fish raise your fins one to three times per day, each session being five minutes long. This is important because the HM's thick tail needs regular exercise in order to strengthen the caudal fin tendons and ensure a strong, "winged" tail shape. This is vital for the proper maintenance of the HM's form.

Read the article: A detailed guide on how to raise a halfmoon betta fish for more details.

6. Breeding

The Halfmoon fish is not the product of a single gene, but rather a combination of many traits which must be present to produce a 180-degree tail. Your best chance for successful halfmoon production is to breed two fish from well-established and reputable halfmoon lines, even if this means paying a premium price for the desired stock. In the long run, investing in quality fish will yield better results than opting for substandard specimens at discounted prices.

If you're unable to find a quality halfmoon within your budget or in the desired form/color, you can begin the halfmoon line with a pair of superdeltas. The odds of getting several HMs in the first generation are higher if the superdelta comes from an established halfmoon strain. Ask for pictures of both parents and fish in the group to ensure that it is a good strain for producing HMs. When selecting your pair, try to get the best ones available; then be prepared to work hard.

Avoid breeding bettas with serious defects, such as humpbacks, tail-biters, and other malformed or unexpected fish. These traits can be inherited and may resurface in your line many generations later when you least expect it. For example, a strain of fish with perfect fins but a weak immune system is not ideal.

Check out the halfmoon betta breeding guide for more information.

Breeding halfmoon betta


The Halfmoon betta fish is a beautiful and unique type of Betta fish that has many different tail types. They are also known to be one of the most aggressive types of Bettas. If you are thinking about getting a Halfmoon betta fish, I would recommend doing your research first to make sure they are the right type of pet for you.

In this blog post, we provided an introduction into the halfmoon betta fish species. We defined what qualifies as a beautiful halfmoon and explored the branching type of Halfmoon. We also discussed how important it is to provide proper care for Halfmoons. Finally, we breeding tips for those who are interested in raising their own Halfmoon colonies. Do you have any questions about Halfmoon bettas? Let me know in the comments below!

Leave a comment

Your email address will not be published. Required fields are marked (*)

Please fill out this field.
Please fill out this field.
Please fill out this field.