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Will Big Koi Eat Smaller Koi?

Koi fish are a colorful species of ornamental carp and popular among freshwater aquarists. In the Japanese culture, they represent good fortune and a sense of spiritual well-being. If you’re considering keeping koi in your tank or pond, you may be wondering about their behavior towards each other. One of the most common questions asked by freshwater aquarists is will bigger koi eat smaller koi?

Koi fish are omnivorous and will eat both plant- and meat-based foods. If the opportunity presents itself, they’ll even eat their own young (koi eggs or baby fry). Basically, any fish that’s small enough to fit into their mouths is fair game, especially if preferred edibles like vegetables and insects are scarce.

Now that you know koi are opportunistic feeders and have been known to eat smaller fish, let’s explore this topic together in more detail. We’ll learn if it’s possible to safely house smaller fish with fish, how aggressive they are towards each other, why they’ll sometimes eat their own offspring, which aquatic creatures make the best tankmates for koi, and what to feed them to keep them well sustained.

So, if you’re ready to learn more about koi fish behavior in captivity – in particular, how they act with others of their kind – then let’s get right to it!

Can You Mix Small Koi with Larger Koi?

If you house your koi fish in an extra-large tank or pond, it’s possible to keep smaller ones with larger ones. The key is to keep them well-fed. If food is plentiful, they won’t feel the need to compete with one another. Competition for food is a leading cause of koi fish aggression. Your best bet to prevent bigger koi from eating smaller koi is to only keep fish of similar size.

Are Koi Aggressive towards Other Koi?

Though koi fish are typically peaceful towards pond/tankmates, they can become aggressive under certain circumstances. For example, if they’re overcrowded or kept in too small of an environment with poor water conditions, they’ll become stressed out and hostile. As well, if they’re under-fed they’ll act aggressively towards each other as they compete for food.

Do Koi Fish Fight Each Other?

Koi fish typically won’t fight each other. Inadequate space, incorrect water parameters, and/or illness may cause this species to lash out at other pond/tankmates. What looks like koi fish ‘attacking’ each other is really them rushing one another in a spawn. This behavior of jumping upon or pushing against one another is normal during the breeding season and no real cause for concern.


Will Koi Eat their Own Offspring?

Koi fish are opportunistic feeders and have been known to eat their own eggs or offspring. Baby fry are particularly at risk which is why the eggs needs to be scooped out of the main tank or pond as soon as they’re laid and placed in a separate aquarium. The youngsters can be reintroduced back into the main tank or pond once they reach juvenile status and are bigger than their parents’ mouths.

Why do Koi Eat their Own Offspring?

It’s important to note that eating eggs and fry are typical of many types of fish, not just koi. The reason being that the adults don’t recognize the eggs or fry as their own. Once the offspring become juveniles and are reintroduced to the pond/tank with their parents, there’ next-to-no chance of them attacking the youngsters.

Do Koi Eat Dead Koi?

Koi fish won’t usually eat other koi when their dead. Unless, if they’re very small and happen to get scooped up in their mouths as they’re foraging along the bottom. Remember, koi aren’t carnivorous. They prefer to eat mainly plant-based foods like algae, vegetables, and free-floating greens with the occasional live ‘treat’ such as insects, tadpoles, and tiny crustaceans.

Will a 15” Koi Eat a 3” Koi?

It’s highly unlikely that a 15” inch koi fish will eat a 3” koi fish. Koi prefer to eat to mainly plant-based foods. Only the tiniest of fish (1/2” to 1” long) are at risk of being eaten. Koi, though large, are a very gentle fish and tend to live peacefully with just about any pond/tankmate. To ensure the safety of smaller fish in a captive aquatic environment with koi, just be sure to feed them enough.

How often should You Feed Koi?

It’s recommended you feed koi fish at least once a day. These fish can grow quite large (between 24 and 36 inches) and need plenty of food to sustain their massive size. Offering them a variety of both plant- and meat-based edibles will provide them with the nutrients they need to live long and healthy lives in captivity. Be careful not to overfeed them, however, as this can negatively affect the water parameters.

What Food is Best for Koi?

A variety of both plant- and meat-based foods are best for koi fish. Offering them greens like water lettuce, spinach, and broccoli as well as protein-rich foods such as insects, worms, and tadpoles will provide them with all the nutrition they need. They’ll also graze upon algae growing naturally in their tank or pond and spend much of their time foraging along the bottom in search of buried edibles.

What Fish do Koi Eat?

Tiny fish that can easily fit into a koi’s mouth are likely to be eaten…albeit inadvertently. Though not carnivorous by nature, koi fish are scavengers and spend most of their time foraging in search of food. Little fish like danios, guppies, and minnows can easily get ‘scooped up’ and eaten if they happen to get caught up in a feeding frenzy.


What Tankmates are Best for Koi?

The best tankmates for koi are fish of like size and temperament. Other koi as well as goldfish are good options. Bottom-feeders like barbs, catfish, tenches, sturgeons, and plecos are a few more suggestions. Just make sure whatever fish you choose is peaceful by nature and requires the same water parameters as koi. Aggressive fish should never be kept with koi as this may unleash their underlying hostility.

Final Thoughts

To sum things up, koi fish are omnivores and will eat both plant- and meat-based foods. As non-picky, opportunistic feeders, they’ll even eat their own offspring. Any fish or aquatic creature that’s small enough to fit into their mouths is considered a potential source. To decrease the likelihood of them eating their pond/tankmates, be sure to keep them well-fed.

I hope this article has been of help to you and answered your questions regarding koi fish and their behavior towards each other in captivity. Thanks for reading and good luck with your aquarium hobby!

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