Do All Koi Fish Get Along With One Another?

Do All Koi Fish Get Along With One Another?

If you’re looking to keep a pond of koi fish, you may notice there are many different breeds of koi. Some types of fish can’t be kept together because they will fight, which begs the question, is it the same for koi fish out in a pond?

Do all koi fish get along with one another? Yes, all koi fish get along with other koi.  Though there are some reports that Koi will eat their own fry, this only happens when they are hungry, or the pond is overcrowded.  Koi also get along with many other species.

In order to keep Koi happy and not fighting, we want to give them sanctuary. So, what else is there to know about how koi fish get along with each other? Well, that is answered next.

Can’t We All Just Get Along?

Generally speaking, Koi are considered peaceful and docile fish that get along well with one another. Unlike Betas, which are not schooling fish, Koi are considered social fish.   Their calm demeanor might be because they are descendants of carp, another fish generally considered calm. Carp can apparently be trained as well, as researchers at the University of Minnesota found.  

However, there are three things to keep in mind:

  • Size of fish
  • The total population of pond
  • Other fish in the pond

Size of Fish

If a Koi becomes hungry, it will do what all animals do—seek out food.  If the fish is small enough to fit in their mouth, it could become fair game.  This includes baby Koi.  

Koi have also been known to eat fish eggs.

The solution?  First, avoid putting tiny fish into the pond (unless you want the Koi to eat them).  Second, make sure they aren’t hungry. Be careful, though. In trying to keep them from going hungry, it’s easy to overfeed them.  Typically, feed Koi enough food they can eat in five minutes. 

It might be tempting to keep feeding them since that will bring them to you, but more than that will not be healthy for them.  And it won’t be healthy for the pond either. Algae blooms, cloudy water, and low oxygen levels can all occur because of overfeeding.

Here are some rules of thumb to keep in mind:

  • Stop feeding them after 5 minutes even if they are making those please feed me some more looks
  • Feed them no more than 3 times a day
  • The number of feedings varies depending on the temperature of the water.  The colder the water, the fewer feedings.

Population of Pond

If a Koi feels crowded, it will lose its calm demeanor and will want some additional living space.  Killing another fish is one way to do that.  

The solution to that?  Make sure the pond is large enough to hold the number of koi that you have.  Sounds simple. Actually, this is complicated because many variables have to be taken into consideration, including

  • Size of pond
  • Oxygen level and filtration system
  • Number of plants
  • How often water is changed

Because of that, most experts will give some general rules of thumb that you might have heard about.  This is one set:

  • For every 10 gallons of water, 1 inch of fish
  • No more than 4 koi per 1,000 gallons of water

Another general piece of advice is to have one Koi per every 500 gallons.  This advice, however, is based on the above variables. The best thing to do is talk to someone local who can assess your pond.

 Other Fish in the Pond

Since Koi are generally peaceful fish, they will get along well with other calm fish.  Here you again want to consider the size of the other fish. For example, although Koi and goldfish are related, a large Koi might find a small goldfish a tasty treat.  Obviously, don’t put baby goldfish in a tank with grown Koi.

Catfish are another fish commonly seen in backyard ponds.  Be advised, though—they grow large, and quickly. They are also more aggressive to smaller fish than Koi.

If you are looking for something more exotic, consider getting a Shubunkins.  These fish can withstand severe weather better than other fish.  They exhibit a variety of different colors, including blue, red, white, and orange, in different patterns.  Unlike Koi, they lack the barbells, or whiskers, of Koi.

How Can I Tell If My Koi Fish Are Fighting?

You might be keeping koi together and notice some of them are chasing others or nipping at their fins. Does this mean they’re fighting, and if so, what do you do about it? Well, the good news is that they actually aren’t fighting at all.

Koi fish are docile fish, and the reason they will chase or nip at the fins of other fish is probably because it is mating season. Male koi will do these things to a female and can potentially damage their potential partners. This is the only time you’ll really see a koi going after another koi unless it’s smaller and can fit in their mouth. (In which case, it will become food.)

When koi chase each other, you don’t have to worry about the females. When the female does get the chance to release her eggs, this chasing motion will allow the males to help her push eggs out since the females have no muscles to do this with.

Battle of the Sexes

One way to cause trouble in a Koi pond is to have an incorrect ratio of male to female Koi.  Most experts recommend that you have a 2:1 ratio. If you have too many males fighting over a female, that can lead to overly aggressive behavior.  Koi breeding is very physical, which is why many people think the Koi are fighting. If you’re not sure what it looks like when Koi are spawning, check out this video.

So, how do you tell if you have a male or female?  The male’s body is slenderer and the fins near his head (also known as pectoral fins) should be a solid color and more pointed than a female’s.  Finally, a male Koi will have a solid line on its underside. Check out this video if you want a more detailed explanation.

Should you not want to have baby Koi, then you need to separate the males and females.  To do that successfully, you will need a separate, spawning pond. Some breeders have a spawning pool which they use to pick which fish they want to breed.  Or you can just decide to have your Koi breed.  

Online calculators can help you with picking how many Koi to have in your pond.  One such calculator can be found here.  Enter the dimensions of your pond, and it will calculate how much water your pond can hold.  

Final Thoughts

Since Koi are not aggressive fish, you can have multiple fish in the same pond, as long as you follow other guidelines regarding the size of the pond, the ratio of male to female Koi, and the other fish you have in your pond.  Remember that an adult Koi can be 24 or more inches long, which is why you want to follow the rule of having no more than one Koi per 500 gallons of water. And if you add other fish, you need to include those in your calculations.   And if you see a couple of Koi getting frisky, you might want to think about if you want baby Koi in your life.


Leave a Comment