Koi Betta Fish: A Care Guide To Help Them Thrive

Koi betta fish are unique and gorgeous fish that appeal to a wide variety of aquarists. It doesn’t matter who you talk to in the fish-keeping scene, many have considered owning these at some point!

Give this guide a read if you’re interested in learning about how to care for koi betta fish, and what makes them so interesting in the first place.

Species Summary

If you’re looking for a show-stopper fish with a punch of personality, the koi betta may be for you.

Don’t let the name confuse you. These freshwater fish are not a cross-breed between traditional koi fish and betta fish. They’re not even a unique species, and still fall under the Betta splendens classification as other bettas. However, this particular variant has a unique coloration that mimics that of prized multicolored koi.

A koi betta fish near the surface

The story of how koi betta fish came about is fascinating. The first koi betta fish were developed in the 1970s by Orville Gulley. Gulley was an inmate at Indiana State Prison and participated in a rehabilitation program that allowed him to breed betta fish. Interestingly enough, he did his breeding in cleaned-out peanut butter jars!

After attempting to create an entirely different betta variant, he realized that the fish had a distinct marbling gene. Gulley sent his newfound marbled koi to famed hobbyist Walt Maurus, and the betta breeding community introduced this beauty to the world!

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Koi betta fish can fetch a pretty penny in the pet trade, but anyone who loves this species will tell you it’s well worth the investment. Whether you keep these fish alone in a minimalist tank or with others in an ornate aquatic environment, koi bettas are sure to be the centerpiece that gets everyone talking.


Koi betta fish have a similar profile to others in the Betta splendens family. They’re small fish with expansive fins that flow in the water like silk drapery.

What makes koi betta fish unique is that signature marble gene. It creates a spectrum of color on the fish. It’s similar to the multicolored nature of some of the most sought-after koi.

Author Note: One unique thing about the marble gene is that it changes. Jumping genes called transposons cause these fish to change color throughout their lives. That makes it more difficult for breeders to determine if they are successful in their efforts, but the unknown aspects of the appearance makes owning koi betta fish so special.

There’s tons of variety with koi bettas. Patches of red, yellow, orange, and black are the most common. But some of the fancier specimens may feature flecks of green and blue. Pair that with the iridescent shimmer that comes with the rich coloration, and you have a living spectacle!

Betta fish are some of the most colorful freshwater fish you can find, but koi bettas are special. Not only do they have that color-changing gene, but the patches of color usually have sharp edges. It’s not a gradual change but a sudden one.

The result is something that looks fit for an art museum!


There are a few different types of koi betta fish available.

The most common is the galaxy koi betta. In addition to red, black, and white patches, these fish have iridescent scales of deep blue and turquoise. Those blue hues usually appear as spots, creating a galaxy-like appearance.

Another popular variant is the candy dragon koi betta. It’s sporting shades of pink, red, purple, and blue.

Koi plakat betta fish are also an option. They can have a myriad of eye-catching colors. However, the most defining feature is the shape of the fins. Like other plakat bettas, their fins are shorter and rounded.


The lifespan of a koi betta fish aligns with that of standard Betta splendens. With good care, they usually live for about three to five years.

Like with any other fish species, high-quality care is a must if you want them to live a long and happy life. Poor living conditions, a lackluster diet, and generally poor husbandry can make the fish more susceptible to health problems and disease, shortening their lifespan significantly.

Average Size

These fish are relatively small. Fully grown, the average size of a koi betta fish is between two and a half to three inches long.

Author Note: It’s worth pointing out that plakat varieties can be even smaller because they lack the silk-like fins of other bettas.

Koi Betta Fish Care

Koi betta fish care is considered to be relatively easy, making them a fine choice for beginners. They’re hardy fish that adapt well to life in captivity.

But of course, these freshwater fish have their unique needs and preferences. Here are some need-to-know care guidelines to help keep a happy and healthy koi betta.

Tank Size

The great thing about these fish is that they don’t require a ton of space. While you certainly won’t find a koi betta living in the wild, they come from wild variants. They live in shallow bodies of water like rice paddies, stagnant pools, and slow-moving streams.

These fish don’t need a ton of room to stay happy. Most aquarists agree that the minimum tank size for a koi betta fish should be five gallons.

If you have the means to do so, consider going bigger. More room is always beneficial. Not only does it give you more opportunities to create an enriching space for your koi betta, but you may be able to keep other fish in the tank (more on that later).

Water Parameters

These fish are the epitome of hardy. Ever wonder why you see them in small plastic containers at your local store? They adapt well to most conditions and can tolerate slight fluctuations without too many issues.

Author Note: Koi betta fish have one unique trait that allows them to survive in conditions most fish can’t. They can breathe in air. These fish have a unique labyrinth organ that will enable them to breathe above and below the surface.

Don’t be surprised if you see your koi betta getting a breath of air at the surface.

Of course, just because these fish can tolerate harsher conditions doesn’t mean that you shouldn’t create a comfortable underwater environment. Fined-tuned water parameters will bring out the best in your fish and make things much easier to keep them healthy.

Check out the preferred water parameters below. Give your tank ample time to cycle and monitor conditions regularly to keep things in the sweet spot.

  • Water temperature: 75 to 84 degrees Fahrenheit
  • pH levels: 5.5 to 8.0 (Around 7.0 is ideal)
  • Water hardness: 4 to 8 dGH (Soft)

What To Put In Their Tank

Koi betta fish like to live in richly decorated environments full of natural decor. Anything that resembles a similar biotype to what wild fish inhabit will do.

At the bottom of your tank, use sand or gravel as your substrate material. These fish have no real preference for substrates, but it’s wise to choose something that can support the health of plants.

Adult galaxy koi betta fish

Plants are a fantastic addition to a koi betta tank setup. They look beautiful, do wonders to improve water conditions, and facilitate the fish’s lifestyle. These bettas love to explore plants, and they often use them for things like breeding and resting.

The best plants for these fish include anubias, java fern, cabomba, and water sprite. Red root floaters and broad-leaf floating plants are great, too. You may even see your betta swimming onto a floating leaf for rest!

To keep your plants healthy, ensure your tank has a suitable lighting system. Good lighting will also bring out the koi betta’s beautiful coloration.

Feel free to add other enrichment items if you have room. Rock caves and smooth plastic decorations add a lot to the underwater habitat and give your fish plenty of objects to explore.

Author Note: Remember to invest in a good filtration system. It should be powerful enough to cycle the tank water several times an hour. However, the outlet should be subtle enough to avoid creating a strong current. Use sponges to minimize powerful water flow and keep the tank relatively still if necessary.

Common Possible Diseases

Koi betta fish might be hardy, but they’re not immune to health problems. They can suffer from all the same diseases and ailments that other freshwater fish encounter. One of the most common issues is Ich.

Ich is a stress-related condition that often arises when bettas live in poorly maintained tanks. It can also happen when the temperature or pH balance isn’t in their preferred range. When stress takes over, the immune system suffers.

Protozoan parasites can then take hold, creating this potentially lethal disease. Ich is characterized by white spots all over the body. Depending on your koi betta’s coloration, those spots can be initially difficult to see.

Unfortunately, Ich is a highly contagious disease that can spread to others in the same habitat. If not treated, it will kill your fish. Thankfully, over-the-counter copper-based medicines are available.

Another common disease to affect koi betta is fin rot. This disease is particularly devastating because it affects the fish’s physical appearance. Fin rot is a type of bacterial infection that often arises when temperatures drop too low.

The bacteria attack the soft tissue of the fins, creating a frayed appearance. The once vibrant coloration can slowly turn gray before sloughing off entirely.

If your fish has fin rot, you can treat it with antibiotics. It’s also important to improve conditions by investing in an in-tank heater.

The best thing you can do to avoid health complications is to monitor tank conditions. Perform weekly water changes and do what you can to keep ammonia levels low.

Food & Diet

In the wild, these fish scour the surface to eat larvae, insects, and other high-protein snacks.

Don’t let that beautiful appearance fool you. These freshwater fish are surprisingly predatory and prefer a diet rich in protein.

One of the most accessible foods you can provide to your koi betta fish is prepared commercial pellets. Betta pellets are readily available at most stores and contain high-quality ingredients to provide a nutritionally balanced diet. Many formulas also contain extra vitamins and minerals to enhance your fish’s vibrancy.

Commercial foods are good everyday items to feed. However, koi betta fish also appreciate foods that tap into their micro predator roots. You can offer bloodworms, mosquito larvae, brine shrimp, daphnia, and more.

Author Note: Koi bettas should eat once or twice a day. During those meals, provide enough food for the fish to consume in two minutes or less. Anything more, and you run the risk of souring the water conditions.

Behavior & Temperament

This freshwater fish has the nickname of Siamese fighting fish. That’s not just a silly nickname. These creatures can be ferocious!

They are some of the most aggressive around, and they will not hesitate to pick a fight with others. Even if you put a mirror up to the glass, the fish’s reflection will cause them to flare its gills up in an attempt to intimidate. Koi betta fish are no different from other betta species. They’re just as aggressive.

Putting more than one male in the same aquarium is out of the question. It’s asking for trouble, and you should never attempt to allow them to cohabitate. A group of females will do fine with one male, but even then, it’s wise to keep a watchful eye.

If you want to avoid aggression altogether, these fish do fine on their own. They don’t require the companionship of others to thrive.

You can observe your fish throughout the day as it explores the tank. It may swim through plants, check out hidden nooks and crannies, and meander about the habitat. These fish can exhibit some weird behaviors.

As mentioned earlier, they love to swim onto floating plant leaves. They may be half-in and half-out of the water when they do so. Many inexperienced hobbyists mistake their fish for dead when they see it.

Author Note: Remember that koi betta fish can breathe atmospheric air. Sitting on a leaf with part of their body above water is perfectly normal, and it’s nothing more than a rest.

Tank Mates

Contrary to popular belief, it’s not impossible to keep koi betta fish with other tank mates. As we said in the previous section, males and females often cohabitate without any issues. Many aquarists will keep a small group of females with a single male.

Females are just as colorful and beautiful as males. But they lack the ornate, flowing fins. As a result, they’re pretty easy to identify.

If you’re considering a multi-species tank, you have a few options. When choosing tank mates, the goal is to avoid selecting any species that resembles another male betta. They become quick targets for the koi betta’s aggression.

It’s also a good idea to avoid fin-nippers. Those fish will only agitate your koi betta and possibly ruin its fins.

The best tank mates for koi bettas are non-territorial passive fish. Some good options include:


Breeding koi betta fish can be a rewarding experience, but it’s also challenging.

You’ll need to set up a separate breeding tank and choose your timing wisely. The best time to breed these fish is when they’re a year or younger but older than four months. That’s when you’re most likely to see success and get fry with the best genetics.

Set up a shallow tank with a divider. The water should only be five inches deep at most. The shallow nature of the habitat will make things easier for fry.

Add your female to one side of the divided tank about an hour before adding the male to the other side. At first, the male will flare its fins like it’s about to strike. Females follow soon after.

Condition the fish with high-protein foods. When ready, the male builds a bubble nest. He may use a plant as an anchor or blow bubbles at the corner of the tank.

You can remove the divider, allowing the fish to spawn. The spawning process can last several hours and looks somewhat violent. Keep an eye on the pair and remove the female if she shows signs of distress.

The female will lay her eggs. After that, males move them to the nest and watch over them. You can remove the mother for safety.

Fungus can cause trouble for koi betta eggs. To minimize issues, consider using antifungal treatments after the female lays her eggs.

The males watch over the eggs until they hatch in 24 to 48 hours. Several days later, they will be free-swimming. Remove the male and allow the young fry to develop.

Feed them infusoria, baby brine shrimp, and other high-protein foods as they grow.

Closing Thoughts

With their fantastic appearance and low-maintenance care requirements, koi betta fish are a great choice for aquarists of any skill level. In fact, we recommend them all the time!

If you’re on the fence about getting these fish, don’t be nervous. There’s a lot to love!

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