Koi Betta: Betta splendens Variation, complete guide

Koi Betta

Koi betta, also known as Siamese Fighting Fish, are a gorgeous type of betta fish with a special gene which causes the fish to have a very cool marbled coloring, and somewhat resemble the famous Koi fish. 


General Information and Introduction 

Betta Splendens             Koi Betta 

The Koi Betta belong to the Percoids order of fish, and the Osphronemidae family. They are a beautiful fish with a very interesting coloration caused by a gene that is very rare in nature. 

The Koi Betta originally come from places like Thailand, Cambodia, Laos, and Vietnam, living anywhere that water could collect like ditches, rice paddies, ponds, and slow moving streams. 

They have a lifespan of around three to four years long, and they are a freshwater fish. This is not a fish for beginners, as it needs close care and dedication to make sure that they are happy, healthy, and stay looking stunning with their beautiful fins and tails. 

More and more people are agreeing that even though these fish aren’t the tamest swimmers, they still don’t deserve to be isolated in a 5-gallon tank to swim all on their lonesome with a few plants. That’s why knowing water parameters and fish compatibility is so important.  

Since having Bettas in a community tank is blowing up, and for good reason, this is your one stop informational guide to all things Betta care, and even understanding how Koi Betta genetics and color layering works. Learn about fin types, how to identify different colors, and prevent diseases like fin rot. All in all, you will get all your info right here, and even some tips and tricks to keep them happy. 

Please note that this is Koi Betta specific, but the care and water parameters will work for any Betta. 

Candy Koi Halfmoon

Natural Habitat 

Since the Koi Betta has the interesting ability to breath out of water, it was naturally found anywhere you found water in Thailand, Cambodia, Laos, and Vietnam. You could find them in rice paddies and slow-moving bodies of water all over Asia. 

 They like warm temperatures and little caves to dart around in, and logs at the bottom. In terms of foliage, real plants are always the best choice, but if you absolutely have to use artificial plants, choose silk instead of plastic. This will ensure that it won’t scratch the fish’s fins and will prevent diseases like fin rot and other bad infections. 


Betta fish behavior 

Betta fish have a special organ called a labyrinth which is a lung like organ that lets them breathe regular air. 

Since they like to swim and move around a lot, they have quite the appetite, but should only be fed one pinch twice a day. 

Bettas are typically classified as aggressive fish, but that only happens when they get territorial or get challenged by a brighter fish or one that doesn’t understand personal space, so make sure to never house two male Bettas in one tank, since they will most likely kill each other, and that is never a good thing. 

Fish underwater red 

Keeping Them Together 

Koi Betta’s are unique in the fact that they do not like to share a tank or aquarium with any other fish, even their own species, since they are quite aggressive and territorial, but if you really want to house them in a community tank, you should put them in a tank setting where they don’t feel threatened, and housing them with the opposite sex is also acceptable. If you decide on a community tank, make sure that the other tank mates are bigger than the betta so that they can defend themselves if it starts to act up, and make it easy for it to mark out its territory. 

A quick pointer is to avoid fish that will nibble on the Koi Bettas fins and tail, since this could result in confrontation, which could result in one of the fish being dead. 

Pick fish that don’t have bright colors, since that could make the Betta feel challenged and need to compete, which could also result in conflict. 

Some suitable tank mates are 

  • Catfish 
  • Guramis 
  • Large Ghost Shrimp 
  • Mollies 
  • Rasboras 
  • Tetras, like the ember and lemon tetras, which we have guides about on our blog already, so be sure to check that out after you finish this post. 

Koi Betta Lifespan

Appearance and Size 

The Koi Betta get their name from the Koi fish, which is a very famous and unique fish, that can get very expensive. The most expensive Koi has gone for 1.1 million dollars, just because of their unique coloring, caused by a very rare gene, that very few species have in the world. One of those rare species is the Koi Betta, which is how it gets its name. The color and pattern however, are not hereditary, since they possess a gene called a transposon. 

To first understand what this transposon does it is important to know what a Koi, or Marble Betta look like. They have splotches of different colors, much like a Koi fish, and no color at all in some places, all over their bodies and fins. 

This is the result of the transposon gene which switches on and off throughout the fish’s lifetime, and creates different types of colors and patterns throughout the body of the Betta. No two Bettas will ever look the same but there are common color patterns for Koi Bettas to grow into, which have their own labels, just so that people know what kind of fish they are getting. For example, a Koi Betta with 3 or more colors is called a fancy betta, while a candy betta is known by their black, red, and blue (or sometimes yellow) color scheme, but Koi Betta not only have special color palettes, they can also have interesting scale patterns and varied fin types.  

Koi Betta Fins


In terms of fins, there are five main categories of tail types. 

The Short-Tailed variety include the 

  • The Wild-type Plakat, which means it has a longer anal fin, and shorter caudal and dorsal fins, 
  • The Traditional Show Plakat, with a longer anal fin that comes down to a point, while the dorsal is rounded and might come to a spade type shape. 
  • Symetrical Halfmoon Plakat, having a rectangular anal fin, short ventral’s, and a caudal fin that commonly grows into a D shape. 
  • Asymmetrical Halfmoon Plakat have either a D or spade shaped caudal, and the anal fin comes down to a point. 

The Long-Tailed Variety are the most beautiful in my opinion, and feature some of the most well-known Bettas. 

  • The Veiltail has all of the fins equally elongated, and the dorsal come to a point. 
  • The Spade tail is exactly what it sounds like, it’s a betta whose tail is shaped like a spade, and is a variation of the veiltail 
  • Roundtails have, just like their name suggests, have a round caudal fin, while the dorsal and anal fins bend towards the back. 
  • Bettas with the Delta fin types have straight upper and lower caudal fins that usually form a 150-degree angle, and the rays are long and straight. 
  • Superdelta, which are pretty much the same thing as regular Deltas, that have longer dorsal and anal fins, and have a wider caudal fin. 
  • Halfmoon Bettas are among the most well-known and one of the most interesting since the caudal fins form a 180-degree fan in a D shape, which almost looks like it connects with the dorsal and anal fins, which are just as long as the caudal fin. 
  • Rosetails are a variation of the Halfmoon, the biggest difference being that the ends of the webbing of the caudal fins ruffles and looks like the edges of rose petals, which is where it gets its name. 
  • The Feathertail also resembles the Halfmoon, except that instead of the fins being nice and uniform, they are branched out and look like feathers you’d find on some kind of exotic parrot, except that parrot is underwater and doesn’t drown. 
  • The last of the halfmoon variations is likely the most fabulous, which is the Over-Halfmoon. The main difference is that the caudal fin is longer and the tail reaches a tail of 185 degrees instead of 180. 

Koi Betta Krowntails

Betta Crowntail

The next group of fin types is the Crowntails, which get their name from a genetic mutation with makes the webbing in between the rays not fully develop and leaves an almost spiked appearance to the edge of their tails. 

  • Single-ray Crowntail looks the closest to the Delta finned betta, just without around half of the webbing closer to the edges, leaving the ends looking strung out. This affects all of the fins on their bodies, including the two ventrals. 
  • The double-ray Crowntail follows the same principle as the above mentioned Single-Ray Crowntail, except that when the webbing ends the rays split into two separate rays which results in a very interesting, almost evil look when paired with the right color schemes. 
  • The Double Double-Ray Crowntail is again pretty much the same as the double-ray crowntail, except that the rays split into four separate, tight knit, splines that extend for around a quarter of an inch. 
  • The Crowntail Plakat is a the crowntail variation of the halfmoon with shorter fins 
  • The Combtail Plakat is like the above mentioned Crowntail Plakat, except for the fact that the rays aren’t sticking out, but more resemble duck feet. 
  • Combtail Bettas are quite similar to the combtail plakat, except the dorsal and anal fins bend backwards towards the caudal fin 
  • The Half Sun Betta is a very spectacular version of the over halfmoon combined with the Combtail Plakat Betta 
  • Cross-Ray Crowntail Bettas are like Double Ray Crowntails except for the fact that the secondary rays overlap each other 
  • The King Crowntail Betta is where the primary rays overlap and never split 


Betta Doubletail

Next come the Doubletails which have their caudal fin split in two, while also generally having longer dorsal and anal fins. 

  • The Doubletail Veiltail looks very similar to a veiltail, but the caudal fin splits in half into a V shape 
  • Doubletail Plakats look identical to Wild Type Plakats except for the split tail 
  • Doubletail Crowntails are a regular Crowntail with a split tail 
  • The Hearttail is when the split in the caudal fin doesn’t reach the body of the Betta, and looks like a sideways heart. 

Rare Mutations are some tail variations that are rare and can’t really be passed down since they are exactly what they sound like, mutations. Some are so rare, there are no published pictures on the internet. Here are the most common of these rarities. 

  • The Tripletail is an offshoot of the doubletail, resulting in a second split. 
  • The apache tail divides the tail into multiple feathers like branches. 
  • Lyretails are a long-debated subject, since some people think that they are not real, and are a result of tail trimming. If they are in fact real, this mutation is when the caudal fin does not reach the usual length. 
  • The swordtail is an extreme case of the Spadetail, causing the end of the spade to grow quite long and look like a sword. 
  • The pintail is very similar to the swordtail, since it looks almost the same, except that the end of the spade is quite thin and not as long. 
  • Bottom Pintails are identical to the regular pintails except that the pintail faces downwards. 


Color Science 

The color of pretty much all Bettas boils down to one big concept. Genetics. The genes of the Betta decide its color, fin type, and also the type of Betta it is. The whole concept of Koi Betta is one gene in particular, called a transposon. This gene is also called a jumping gene, which is a DNA sequence that jumps around the genome, resulting in splotches of pigment and color around the Bettas body and fins, like a Koi Fish! This means that no Koi Betta is guaranteed to hold its color throughout its lifetime  

Multi color fins

Pretty much every possible color a Betta can be is

  • Royal Blue 
  • Steel Blue 
  • Turquoise 
  • Turquoise (Green) 
  • Red 
  • Extended Red 
  • Orange 
  • Yellow 
  • Melano 
  • Brown 
  • Black Lace 
  • Cellophane (Transparent Fins) 
  • Purple 


Caring for your Koi Betta

Candy koi fish 

Koi Bettas can get their fins and tail cut or scratched very easily, since the fins are very fragile and delicate. They are most often damaged and scraped by the other fish in their tank, which is why you should think carefully about who you put in their tank. Sharp substrate is also an issue but if you stick with smooth pebbles and sand that issue should solve itself. It’s very important that you check them for cuts and scrapes, and treat them before they get infected. 

They are unfortunately prone to Lymphocystis which is a viral infection that starts out as white dots all over the bettas body and turn into cauliflower looking growths. 

Their beautiful fins and flowing tails are a double-edged sword, since their amazing and breathtaking velvet like fins make them susceptible to fin rot, which is as pleasant as its name suggests, which is why it is very important to make sure that their water filtration system is cleaning the tank at all times to prevent this horrible and painful disease. 

Beautiful fins

Aquarium Size and Specifications 

One thing to get out of the way is that Bettas of any kind do not like loud noises in any way shape or form, so make sure to set up your tank in a nice and quiet place to help reduce stress. Another thing to note is that Bettas like to jump when they get close to the top of their tank or body of water, so make sure that you have a nice tight fitting lid to prevent this. 

When setting up your tank, you should always start with the substrate, which should be nice and soft or something without sharp edges, so that they won’t catch their fins and tear them. Things like sand and pebbles should be sufficient, just make sure to lay about one to two inches on the bottom of whatever tank you are using. You could take a look at our Tank Guide. 

Good filters are important, so please don’t attempt to keep Bettas without one. Make sure that the filter you get doesn’t disturb the water since Bettas like nice still water to recreate their natural habitat of puddles and ponds. 

In terms of lighting, they like bright, lights like LED’s and fluorescents directly over top of the Bettas and actually prefer artificial lights to natural sunlight. 

Investing in a submerged water heater is a must, since these fish require tropical temperatures to live. 

Bettas quite like plants, both rooted and free-floating plants will work great, and live plants are much more desirable than artificial plants, since they won’t scratch the fish. 

Galaxy Koi image

Bettas require consistency in their water conditions, since any sudden or drastic changes can seriously harm them, even if you are within their safe parameters, can cause serious illness or death. Make sure to check water levels regularly, and dechlorinate the water to make sure that your ammonia levels stay low. This is another reason that live plants are crucial, since they help regulate harmful substances like ammonia. 

Water parameters should be followed quite closely to ensure that your betta is as happy as can be. 

Ph levels should not exceed 6-8 

Water hardness should be 5-35 dGH 

Nitrate should be less than 40 ppm 

The nitrite levels should be at 0 ppm 

In terms of water temperature, you should be looking at 74 to 81 degrees Fahrenheit, which is 23.3 to 27.2 Celsius. 

You should be doing a weekly 25 percent water change and you should run a complete water cycle before introducing your Bettas to the tank. 


If you are making home for a single Betta, you should have a 5-gallon minimum tank. A betta in a community tank should be no less than 15 gallons depending on what kind and how many other fish you are keeping with it. 

Fish tank


Your Koi Bettas health depends heavily on their diet, and helps them be happier and more active. A good way to gauge how well you are feeding your fish is by how active your fish are, and if you are doing a good job of this, you will notice that they are less stressed, and are keeping their color, and even getting more vibrant and beautiful. 

Since Bettas are carnivores, people make special flaked food made specifically for them, but it is still good for them to have the occasional live treat, such as a bloodworm or brine shrimp. 

Feed your bettas a pinch of flaked food twice a day, but don’t overfeed them. I have gone on before about how bad overfeeding is, and what the side effects may be. I won’t list them here, but I did go over them on the Ember Tetra post, but I think this is enough of a warning to not overfeed them. If your Bettas are swimming abnormally or are showing less energy, this is a sign that they are getting too much food and it is safe to withhold them for a day to give them time for them to get back to normal. 


Koi Betta Breeding and Gender differentiation 

While the differences between male and female Bettas vary from species to species, but the most common way of differentiating them is the fins, as they are most commonly larger and longer on males than on females. 


Do you want Koi Betta in your fish tank? 

If you are looking for a beautiful species of fish resembling the all famous and very expensive Koi fish, then by all means go for it! But with breathtaking looks, come some difficulties, such as extensive care. This isn’t the easiest species to take care of, so make sure that you know what you are doing first and rack up some experience and make sure that you are ready for a fish of this caliber. 

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