Why is My Koi Fish Not Eating?

Koi is a freshwater fish and a lot of people keep it in ponds and aquariums for its ornamental value.

Caring for a koi fish is not complicated, but they have precise requirements. If the conditions are not met, your koi fish can show changed behavior.

A koi fish’s feeding habits can change because of many different environmental factors.

If your Koi fish is not eating, it may not always be something to worry about, but it is vital to find the root cause of the issue.

Koi Fish Not Eating – Possible Reasons

Koi fish is an animal with eating habits like any other– they require feeding one or two times a day.

A koi fish takes up to five minutes to finish its meal. Like any other animal, if your koi fish refuses to feed, there could be an underlying problem.

Below are some of the common reasons your Koi fish may be refusing to eat.

Reduced Temperature

A koi fish’s eating pattern depends a lot on the temperature of the water they live in.

Usually, they feed more during the summer when the temperature is high. At higher temperatures, the koi fish can feed between two to four times a day.

As the temperature starts dropping in fall, their appetite starts to decrease with the decrease in temperature.

At 68 degrees, a koi fish will only require feeding once a day or twice, with a lesser quantity of food.

At 50 degrees, its food requirement decreases even further. Below this temperature, the koi carp will require eating only twice a week rather than twice daily.

A koi fish’s decreased appetite in colder weather is hibernation.

A koi fish hibernates in low temperatures and stops eating entirely due to its metabolism slowing down.

Living in an Ecosystem Pond

An ecosystem pond is a natural environment consisting of various plants, algae, insects, and animal species.

It is a balanced ecosystem with a complex food web. It is self-sustaining and requires little to no maintenance.

If you built your ecosystem pond, you can install mechanical filters and add your choice of fish to it.

Various fish, turtles, and frogs thrive in ecosystem ponds. Algae, plants, insects, and birds are automatically attracted to this ecosystem.

The food chain that is established in these ponds is balanced.

Any koi fish that lives in this ecosystem is a part of that food chain and does not require feeding from an external source.

If the environment (pH, temperature, etc.) remains unchanged, the koi fish will thrive in the pond.

If your koi fish is not feeding, it is nothing to be worried about!

It means your koi fish is probably filling itself with delicious insects in the water. You can skip giving them food for two to three weeks without starving them.

Also read: Do Koi Fish Eat Algae? Do’s and Don’ts!

Reduced Amount of Oxygen in the Pond/Tank

Low oxygen is a common reason why your koi fish may be eating less (or not eating at all).

You can solve this problem by regularly giving small amounts of food until the oxygen level fixes naturally.

You can also consider installing an air pump that can help oxygenate the water.

Underlying Disease

Inactivity and lack of hunger are the most glaring signs of disease. As they become tired due to illness, they will start remaining out of your sight.

Notice that your koi fish is disappearing at times and also showing symptoms such as swimming near the surface, gasping for breath, bumping against items, or the color of their bodies becoming lackluster.

It could be a dead giveaway that they are ill.

Lack of appetite is one of the first few signs of disease. Most koi fish can get better without intervention within a few weeks at a time.

However, it is better to take it to the vet immediately as some koi fish do not improve on their own and may die if not checked soon.

The most common diseases infecting a koi carp may be costia, fin rot, dropsy, anchor worms, etc.

Unfavorable Condition of Water

There is a simple way to determine whether water is the reason behind your koi fish falling ill.

If you have more than one koi fish in the pond, you will have to observe all of them and notice if they are healthy or not.

A single koi fish not eating can be due to many factors such as disease or strain.

However, if all the koi fish face the same problem in the pond, it could be a problem with the water environment affecting them all.

A water tank that has not been cleaned and has ammonia and other toxins built up over time may cause low appetite and inactivity in your koi fish.

If the problem is not addressed in time, all of your koi fish could die.

Ways to Correct A Koi Fish’s Feeding Problems

Improving the Quality of Water

Koi fish are delicate creatures that require particular conditions to live; if they are not met, they may die.

They are susceptible to sudden environmental changes, which may stress them out. When they are stressed, they stop eating.

As mentioned above, lower quality water affects your koi fish’s feeding habits. The natural waste products of all living creatures have nitrates and nitrites.

When these waste products decompose, they release ammonia, a toxic byproduct.

An ecosystem naturally contains bacteria that keep the ammonia levels in control. However, they may build up sometimes and cause the water to become contaminated, affecting the living population.

Increased levels of ammonia in the water cannot be observed visually.

You will need to buy a chemical water testing kit that can detect if the levels of ammonia are increased.

Ammonia is a substance with a high pH. If ammonia has built up in your koi fish’s tank, the pH of the water is probably higher than it should be. Sudden changes in pH are not suitable for your koi fish’s health.

This is why keeping a check on the ammonia levels in water is very important as they also affect the pH and KH of the water in the pond/tank.

A koi fish cannot survive such stressful conditions; after a prolonged period of not eating, it dies.

Oxygenating the Water

Any stormy condition can cause an immediate drop in the oxygen levels of ponds.

Similarly, fewer aquatic plants or algae could also cause oxygen deficiency as there are not enough plants to carry out photosynthesis.

You can introduce oxygen directly into the pond or tank by aeration.

Bubbles in water are a sign of oxygen in the tank, and your koi fish should start eating again in no time!

Changing the Feed

Giving your koi fish the same type of feed for so long may be why they are turning their noses up at the mention of food- they are also living creatures, after all.

If you think your koi fish are just being particular about their feed and have no serious underlying problem, you can try switching up their meal a bit.

Koi fish prefer high protein levels in their diet, which should be from an aquatic rather than a plant source.

While they can also survive on plant-based sources, it is not very practical.

It would help if you switched up your koi fish’s diet so that they can get adequate nutrition, such as vitamins and minerals.

You can treat your koi fish every few weeks with some organic insects such as silkworms. It can be healthy and delicious for them in little quantities.

Treating the Underlying Disease or Problem

If your koi fish lives in a pond, it is easy for parasites and other harmful insects to make their way into it.

Parasites or predators can harm your koi fish; once sick, it will hide from you, not even coming out to get food.

A few noticeable signs of a koi fish with an infection are

  • Slow movement
  • Decreased appetite
  • Lackluster skin color
  • Hiding
  • Apparent wounds or signs of injury

Parasitic infections are easy to treat. You can pour a wide-range parasite medicine into the pond to cure it.

These medicines also work as a preventive treatment, and you can use them once or twice a year, even when your koi fish is not sick.

Final Words

A koi fish can stop eating due to many different reasons. If the weather is cold, it can be because they’re going into hibernation.

If that is not the case, your fish could be stressed due to an underlying problem you will need to figure out.

Check for diseases and water quality and get it checked immediately instead of force-feeding your pet.

You can prevent your koi fish from getting sick by regularly checking them and maintaining their tank. Good luck!

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