5 Best Koi Tank Mates – FishLab

Are you looking to add some companions to your koi pond or aquarium? Koi fish are not only beautiful but also make fantastic community fish. Whether you’re maintaining an outdoor pond or an indoor tank, choosing the right tank mates for your koi is crucial for a harmonious aquatic environment.

The best koi tank mates are fish that thrive in the same crowded conditions and peaceful water environment as koi. They should be non-aggressive and able to coexist comfortably in the same water parameters.

The best koi tank mates are fish that are just as happy and satisfied in a crowded pond as koi themselves. No aggressive fish should be added. The tank mates of a koi should also be able to survive comfortably in the same water conditions as the koi.

In this article, we’ll explore the top fish species that make excellent companions for your koi. We’ll discuss what makes each of these fish a great choice and provide guidelines for selecting the best tank mates.

Koi Tank Mates – What You Need to Know

There is a lot to understand about caring for a fish, and when you decide to add more than one type of fish to the mix, things can get complicated quickly. Don’t let this overwhelm you! Let’s take a look at all your koi fish will need, as well as the criteria for the best koi tank mates!

Temperament

Koi are typically very social, peaceful fish. You have probably seen koi in a local koi pond and noticed that they have no personal space issues. Several koi can be clustered around one another or even right on top of each other with no fighting to be seen!

They are even social with people, sometimes swimming to the surface to get a pat on the head. That being said, not every fish is as gentle and peaceful as the koi. It is critical that you find fish which are just as peaceful in temperament if they are going to share space with your koi fish.

Size

Koi fish can get up to 15 inches long, which is pretty big for any aquarium fish, but some can get even larger. There are “Jumbo Koi” variants that can get larger than 30 inches long!

Due to the size of the koi you do not want fish which are much smaller than 10 inches in length to live in the same space. With only a few exceptions, any fish that are smaller than 10 inches can run the risk of being eaten by the koi, or at the very least, feeling crowded by the larger fish.

If you do have fish that are much smaller than your koi, such as guppies, you will need to make sure the tank has plenty of places for those fish to hide. Make sure your koi are sufficiently fed so that the koi does not feel the need to hunt for smaller fish.

Competition

Koi are very easily pleased when it comes to food. In fact, koi fish tend to eat both plants and meat. They love shrimp and smaller fish. However, they will also be happy to eat plants and algae, and usually enjoy a mix of veggies and food to stay healthy.

When it comes to tank mates that will make a koi fish’s life better instead of worse, you need fish that eat differently. Whether their feeding is at a different time, or they simply like different kinds of food, you need fish that won’t steal too much nourishment from the koi or vice versa.

Parameters & Tank Setup

One of the most important things about a koi’s tank is that it should be set up in a half-shaded area or in a very quiet place. Additionally, koi fish need large substrata, and they can only survive in temperatures between 59 and 77 degrees Fahrenheit.

It is also important to have both “hills” and “valleys” in the koi environment, meaning some areas of the floor of the tank should be higher than others so that there is a sense of depth and shallow waters.

With all of this, your koi and any tank mates who enjoy the same tank parameters should be happy and healthy! Just be sure that the tank itself is at least 100 gallons; remember that these fish get very large, and their tank mates will need plenty of room.

Best Koi Tank Mates

1. Suckermouth Catfish
2. Goldfish
3. Guppy
4. Chinese High-Fin Banded Shark
5. Redear Sunfish

Let’s take a look at every fish that might work as a good tank mate for koi.

Check out these other similar posts:

• Porcupine Puffer Tank Mates
• Rosy Barb Tank Mates
• Black Moor Tank Mates

1. Suckermouth Catfish

• Scientific Name: Hypostomous plecostomous
• Adult Size: 2 feet
• Compatible With: Koi Fish
• Care Level: Easy
• Origin: South America

There are actually more than 600 species of suckermouth catfish, but you will probably only find a few in pet circulation. These are sometimes called plecos or by their longer scientific name, plecostomous. Common plecos are known to grow up to 2 feet in length.

Suckermouth catfish are named for their downward-facing sucker mouths. They use these to feed on algae and debris that may be stuck on substrate, decorations, and even to the side of aquariums!

Suckermouth catfish are largely peaceful and they are dark colored with even darker muddy-brown spots. Their heads are long and pointed. They have the bonus effect of cleaning up any leftovers that a koi leaves on the bottom of the tank after meal time!

Pros of keeping with Koi:

• No aggression
• No food competition
• Cleans up bottom of the tank
• Stays near the bottom of the tank

Cons of keeping with Koi:

• None

2. Goldfish

• Scientific Name: Carassius auratus
• Adult Size: 14 inches
• Compatible With: Koi Fish
• Care Level: Easy
• Origin: Eastern Asia, China, Japan, Europe

These are favorites for many aquarium builders. In addition to being the classic, stereotypical fish kept by community tank-lovers everywhere, these fish are noted for their beauty. Despite the name, goldfish can be found in a variety of colors and body types.

For example, some goldfish are orange with white speckles in a dreamsicle-like pattern. Others are entirely orange, while still more are yellow or almost entirely white. Goldfish like to be in schools with more of their own kind, but this is not the only option.

Because goldfish are peaceful, the only obstacle in taking care of goldfish is making sure that they have plenty of filtration and room in the tank. Other than that, they do not steal koi food, and they are under no danger of being eaten unless they’re not fully grown when added to a koi tank. Another reason goldfish are often paired with koi is because both species can withstand cooler water temperature than the average tropical fish. This makes them an ideal candidate for outdoor ponds.

Pros of keeping with Koi:

• No aggression
• No food competition

Cons of keeping with Koi:

• None

3. Guppy

• Scientific Name: Poecilia reticulata
• Adult Size: 2 inches
• Compatible With: Koi Fish
• Care Level: Difficult
• Origin: South America

Guppies are very small when compared to koi, it cannot be denied. This makes them pretty dangerous to keep as koi tank mates, but not impossible. After all, they do thrive in most of the same tank conditions and they are peaceful; however, their size is what makes it risky to keep them with koi.

Our recommendation is to make sure there are plenty of plants and places for guppies to hide. At the same time, feeding times should be staggered, but plentiful, so that the koi do not feel it necessary to hunt down the guppies.

Other than that, guppies are a joy to have in the tank! They are small, and males tend to be even more colorful than females, but they are nonetheless beautiful. They can be in just about any color of the rainbow, and you can even find a preference in tail shapes and lengths, too.

Pros of keeping with Fish Name:

• No aggression
• No food competition

Cons of keeping with Koi:

• May become koi prey

4. Chinese High-Fin Banded Shark

• Scientific Name: Myxocyprinus asiaticus
• Adult Size: 24 inches
• Compatible With: Koi Fish
• Care Level: Easy
• Origin: China

This fish is one of the most interesting, exotic, and sadly, underrated fish in the freshwater aquarium scene! Chinese High-Fin Banded Sharks are named for their markings, not for their actual status as a shark. Actually, sometimes they are called “Chinese Sailfin Suckers” or “Topsail Suckers” instead.

They can become quite large, living up to 15 years old. They are very peaceful and mild in temperament, which makes them great for koi tank mates. Actually, the way a Chinese High-Fin Banded Shark looks before growing old is remarkable.

As juveniles, this fish is absolutely beautiful. They do not seem like they can get much bigger than a few inches (although they do) and they are usually stark white and black striped. When they get older, the stripes almost completely disappear and are replaced with a solid color. Though they change in appearance, their temperament stays peaceful.

Pros of keeping with Fish Name:

• No aggression
• No food competition

Cons of keeping with Koi:

• None 

5. Redear Sunfish

• Scientific Name: Lepomis Microlophus
• Adult Size: 12 inches
• Compatible With: Koi Fish
• Care Level: Medium Difficulty
• Origin: United States, Mexico, Morocco, Puerto Rico

This fish is highly popular in the fishing world and commonly caught and kept for food. However, they are also great pets when they can be accommodated with the right tank size (a minimum of 50 gallons) and tank mates like the peaceful koi fish!

Redear sunfish get their name from the dark spot behind their gills that is lined with a sliver of orange or red coloration. They have a few variations like the Pumpkin Seed Sunfish and the Green Sunfish, but generally, they are a narrow type of fish with green, black, or gray bodies. Sometimes these are highlighted by brighter orange or red markings. The speckles on their skin and the spikiness of their fins contrast beautifully with the more streamlined or vibrant koi.

In addition, redear sunfish are not energetic in the daytime, preferring to explore the middle of the tank only at night while coasting in a relaxed state while the sun is up.

Pros of keeping with Fish Name:

• No aggression
• No food competition

Cons of keeping with Koi:

• None 

In Conclusion

To sum it all up, the best koi tank mates are fish that can handle the same water parameters of this pond-kept fish. They should not only be able to handle the same temperature range and water hardness, but they should be compatible with the social and peaceful nature of a koi fish.

If a fish has a similar temperament with the koi, all that is left to do is make sure they do not out-compete one another for food. As long as you have a good idea of the similarities between a koi fish and their tank mates, such as those between the koi and the golden orfe or the suckermouth catfish, you’re on your way to having a great and peaceful koi tank!