Why Koi Fish Chase Each Other in a Pond

Koi are the ultimate ornamental fish for various reasons. First of all, the coloring and patterns of their scales make them gorgeous. Second, they’re extremely resilient and have been bred for centuries to adapt to many climates. Finally, koi are known to be docile for the most part. For example, the popular chagoi breed is known to be friendly to the point that it will enjoy being fed by hand. When you have chagoi in your pond, other koi will become more curious and gregarious. Even though koi aren’t schooling fish, they sometimes enjoy swimming next to their aquarium mates, but there may be other times when they’ll chase each other around. The knowledgeable staff at Aquatic Warehouse, a trusted provider of koi pond supplies, offer a few reasons you may see chasing behavior in your koi pond.

Breeding and Spawning

This is the most common reason you’ll see koi chasing each other, and it will likely happen during the middle of spring when the water is starting to warm up. This change in temperature results in a hormonal change for both males and females, and this is when the chase starts. There really isn’t that much mating among koi. Females appear pregnant because they’re filled with eggs they cannot release on their own. The chase is a prelude to bumping the female around plants and rocks so the spawning process can take place.

Competing for Females

Even if you have two couples in your pond, the males may still compete with each other for both females. The size of male koi will have a lot to do with this behavior. A larger male will want to show off by chasing smaller koi around, but this will very rarely devolve into serious aggression because females eventually spawn on their own. In some cases, a pregnant female may be accosted by another female for the purpose of releasing eggs.

Bored or Stressed Koi

This is the most significant reason you should stock your garden pond with substrate, rocks, plants, and decorations. A pond that only features water and fish is the most unnatural place for koi to live in, and this will eventually confuse and stress fish because they’ll feel as if they don’t have anything else to do but feed and swim around in an aquatic space with unnatural borders. At some point, the fish will become afraid of shadows, and they may swim around in what looks like chasing but is actually frantic behavior. Stress from poor water quality is also a trigger for breeding. Sounds strange but it’s true. When stressed, all animals have a higher reproduction rate. Think “this could be the end of my species” mode. A lot of people think that because their fish are spawning that they’re doing everything right. However, it’s usually the opposite.

An Unhealthy Ecosystem

Similar to the situation above, a pond that has become overrun with algae bloom, high ammonia levels, or fungal infections will cause koi to behave erratically. When koi are sick, they may feel as if their pond mates stand in the way of survival, thus resulting in chasing behavior. You may also see this happening in a pond that has gone through a period of underfeeding.

To keep your koi happy and healthy for many years to come, it’s crucial to have all of the necessary supplies on hand. At Aquatic Warehouse, you can purchase everything you need, from koi pond filters and pumps to nutritious koi food and beneficial bacteria. To speak with one of our friendly representatives, please give us a call today at 858-467-9297. You can also take a look at the products on our website or stop by our store in Kearny Mesa.