What Fish Can Live With Koi in a Tank? (6 Koi Tankmates)

Koi are peaceful and social by nature, so they’re ideal tankmates for other fish species. However, in order for all the aquatic creatures to live in harmony, you’ll have to take into consideration factors such as other fish’s nature, feeding habits, and water parameter requirements.

Then, what fish can live with koi in a tank? In short, koi fish live with other fish that are roughly similar in size, feeding habits, nature, and water parameter requirements. Some examples are goldish, golden orfe, and barbs.

Please continue reading to learn what other fish can live with koi.

The Best Candidates for Koi Fish Tankmates

Koi are coldwater fish that are opportunistic omnivores. Although they are not aggressive, koi can eat organisms smaller than them (even if it means their fry). Aspiring koi fish keepers can check out the following fish species as suitable candidates for a koi tankmate.

1. Common Goldfish

No other tank mate is more ideal for koi than the common goldfish. After all, these two fish have the same ancestor – the Asian carp. They might look different, but goldfish and koi get along like jelly and peanut butter.

Goldfish thrive best in 68- to 76-degree waters and require nearly the same water depth as koi (a minimum depth of 4 feet, as opposed to koi’s 3-feet-minimum need). They are easy to care for, and their vibrant color never fails to draw a smile from anyone who sees them.

Feeding these two species is never an issue because koi can eat goldfish flakes, while goldfish can devour koi pellets. So, it is unsurprising to see koi and goldfish live together harmoniously and peacefully in the same tank.

2. Golden Orfe

A Baltic Sea native, golden orfe make a suitable tank mate for koi. Although this fish can grow bigger than koi, its peaceful nature makes it a suitable companion in the same tank or pond.

Speaking of “home,” you can forget this fish species if you are only going to keep it in an aquarium. Like koi, golden orfe fish thrive best in larger bodies of water, such as ponds. Hence, their minimum requirement is 500 gallons, although you can settle for 300.

Orfes need higher dissolved oxygen levels than koi. You might want to consider this factor in your koi fishkeeping plans. On the bright side, you will never worry about the golden orfe nipping at the fins of a butterfly koi.

3. Barbel

Barbels are another suitable tank mate for koi in tanks. These Western European fish can grow up to 18 inches, about the same size as koi. Their olive-brownish bodies feature large scales for protection, although they do not need them with the koi’s docile nature.

As a bottom feeder, Barbels thrive on flakes, sinking pellets, bloodworms, and small shrimp. Sinking pellets and algae wafers are an appetizing treat, which Barbels can share with koi.

Ideally, you will want three Barbels in the tank because nothing beats swimming around the pond or aquarium with your friends.

4. Suckermouth Catfish

Here is a species that answers the question, “can janitor fish live with koi?” This South American catfish is not only koi-compatible but is also an amazing tank cleaner.

Its bottom-facing mouth allows this catfish to scrape the tank substrate and walls, removing algae and other organic debris. Its specially-designed oral cavity enables the Suckermouth to create a suction on the aquarium wall.

Despite their size, Suckermouths are perfect tankmates for Neon Tetras and Platys. If these catfish do not mind living with these small fish, they should not pose any safety issues when you put them with a koi.

5. Large Barbs

Colorful and hardy barbs make suitable koi tank mates. Found in Asia, Europe, and Africa (although originally from Sumatra, Indonesia), barbs range in size from 2.5 inches (i.e., Black Ruby) to 14 inches (i.e., Tinfoil barb).

We recommend sticking with larger barb species (i.e., the 6-inch Denison barb, the 6-inch Rosy barb, and the 14-inch Tinfoil barb) for your koi. Although these fish do not threaten koi, they could be on the koi’s menu if you are not careful.

You can feed barbs with the same food as koi. Ideally, you will want at least five barbs to foster their shoaling behavior.

6. Chinese High-fin Banded Shark

Although it may seem strange that a shark can be  a fish compatible with koi, the Chinese High-fin Banded shark (a.k.a. Topsail Sucker) is a peaceful bottom-dweller. Therefore, though it may grow up to 24 inches, it will not harm your other fish whatsoever.

Topsail Suckers thrive in 62- to 82-degree waters, making them suitable tankmates for the coldwater koi. They need plenty of hideouts to avoid running into koi, although the Chinese High-fin Banded shark will relish an open space to swim around.

Juveniles look very stunning with their black bands over white bodies. A 55-gallon tank is sufficient for these friendly sharks, although 300 gallons is the absolute minimum if you want them to live with koi in ponds.

Tips to Choose Koi Tank Mates

Although a koi fish compatibility chart can help you determine the most suitable tank mates for your koi, the following tips can increase your chances of picking compatible koi fish tank mates.

1. Koi are friendly. Hence, they need non-aggressive and social tankmates to ensure everyone is happy. You do not want a territorial fish that will fight the koi.
2. Koi are coldwater fish, thriving in an aquatic environment with temperatures between 59 and 77 degrees Fahrenheit. Koi tank mates should also live within these temperatures.
3. Pay attention to koi tank mates’ pH requirements. As kois do best when the water’s pH levels hover around 7.2 to 7.4, other species’ needs should be similar as well.
4. Pick tankmates with a similar size to koi. Hence, you can choose a large fish species for a large-sized koi and small fish for small koi.
5. Koi tank mates should mimic or complement koi fish behavior in aquarium units. For instance, tankmates should not fight over food, bite the koi’s fins, or do other aggressive stuff.
6. Other fish species must require the same level of care as koi or less. You will want koi to be the focus of your fishkeeping journey.

What Fish Cannot Live With Koi?

Although koi are peaceful, they still adhere to the unwritten rules of the food chain. Anything smaller than a koi is potential food. However, we should never see this as aggression, but as a natural part of life.

In some cases, the issue is not about the food chain but habitat differences. Koi thrive in cold water, while some species live in “heated” water. So, here is a list of fish that cannot live with koi.

1. Guppy fish – Guppies are tiny, growing only up to 2.5 inches, so they’re susceptible to becoming koi’s food.
2. Mollies – Some Molly fish (i.e., Sailfin) are large enough to escape becoming a koi’s dinner. However, most mollies are only two to six inches and thrive in slightly warmer waters.
3. Tetras – The average aquarium Tetra only measures about two inches. Some Tetras are also predatory (i.e., bucktooth and piranha), subjecting koi to potential harm.
4. Angel Fish – Angelfish are not only smaller than koi. They also need warmer water temperatures.
5. Parrotfish – Parrot fish is another species that cannot live with koi because they require warm aquatic environments.
6. Other fish – Minnows, Danios, Fancy goldfish, Barbs, small catfish species, juvenile fish, and fry are at high risk of ending up on the koi’s dinner plate.

FAQs

Can turtles live with koi?

Yes, turtles can live with koi. However, there are some precautions.

1. Pick less aggressive turtle species, such as a red-eared, musk, yellow-bellied, or painted.
2. Ensure to feed the turtle well to avoid competition with koi.
3. Turtle species are destructive and dirty. Hence, you might want to invest in a high-quality pond vacuum and filter while planning the aquascape.
4. Always quarantine the turtle before introducing it to koi because this amphibian carries many bacteria and parasites.
5. Make your koi pond escape-proof because turtle species are escape artists.
6. Add basking areas for a turtle to keep it happy.

Can I put koi in an aquarium?

Yes, you can put koi in a fish tank. However, unlike koi in a pond, you cannot expect these fish to grow their full size. You might undermine koi’s well-being, growth rate, and longevity.

Check out this aquarium size chart to determine how many koi you can place in your fish tank.

Conclusion

What fish can live with koi in a tank? The common goldfish remains the best candidate for a koi tankmate. Other suitable alternatives are barbs, golden orfe fish, suckermouth catfish, barbell, and Chinese high-fin banded shark.

You can expand your tank mate choices by researching non-aggressive fish species, preferably with nearly identical water quality tolerances and feeding requirements as koi.

Although koi are peaceful, their “food chain-related instincts” can still kick in and harm small fish species.