Koi Fish Care – Simple and PRACTICAL Tips and Tricks

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There’s no greater feeling in the world than to reach home to something so sublime it swirls your worries away. Koi fish is undeniably the most adorable fish to pet because of their vivid, catchy colors and energetic nature.

Keeping Koi as a pet has become customary, especially for Zen gardens, spas, and garden ponds for their beautiful appearance and pleasant personality. 

So, if you are someone who’s been thinking to keep Koi as a pet animal. Pat yourself on the back for an amazing decision that you’ve made. However, before domesticating Koi fish, there is a whole lot of work and research needed because they tend to be more suitable for natural ponds than aquariums. 

Koi Fish Care Tips

Here are some tips to keep novice Koi parents well-acquainted with the basic requirement of Koi.


If you’re concerned about the asset, know that Koi fish can be kept in aquariums and natural ponds. However they are not your average aquarium fish or common carp.

Koi are the happiest in their natural pond habitat because of several reasons.

1. Koi are prolific parents. Koi reproduce thousands of eggs during their mating season1. Therefore, a vast pond would be ideal for keeping your shoal of Koi in harmony. 

2. Koi are energetic and playful pets. The size of the pond must be enough for them to play around with each other. Also, the Koi are quite aggressive when it comes to overcrowded places. So the area and depth of the pond must be taken into consideration before stocking too many Koi fish.

3. Koi fish attract predators. To keep them secure from predators, a pond at a depth of three to four feet is highly recommended to provide Koi with safe hiding and resting places. Installing netting over Koi ponds prevent the predators and scavengers from hunting your valuable Koi.

4. Koi can grow rapidly. Koi show a great tendency to proliferate, and therefore, they require a vast, warm habitat to keep growing healthy and happy.

5. Koi diseases. Koi are prone to diseases such as Ich (white spot disease). To fight these disorders, Koi pond needs to be well maintained with a water filter system installed to keep bacteria and viruses away from the pets.

There are two routes to building a Koi Habitat, either you hire a professional or you DIY. If you DIY, take a look at our best koi pond kit post for recommendations on quality setups on non bottom drain installs.

Looking for the best koi fish to buy? Check out our Best Koi Fish post. NextDayKoi is our recommended retailer. Use ASDEPOT at checkout to get 10% off!


Koi Food For Ponds

Did you know?

Koi are omnivorous. As such, Koi need plants and meat in their diet. As a Koi owner, you should know the right kind and amount of food. Koi fish are avid eaters. Therefore, you need to feed them quite often.

The market is flooded with Koi food. However, younger Koi fish need more protein diet than adults, so if you’re domesticating the young ones, buy the food formulated for young and small Koi. Like humans, Koi fish also get bored with the same food. Therefore, the variety is imperative. Also, there are different nutritional needs of Koi for different seasons. So, proper research is the key to buying Koi food. Want to learn more about the best koi food? Check out our post in the link!

Unfortunately, Koi are aggressive with aquatic plants. So you should implement safety measures to prevent any hazards. Don’t keep any plant that might be harmful to Koi in the long-term.

Note: Don’t overfeed your Koi fish. Otherwise, it might create health problems. Feed in small quantities, but do it often to avoid leftovers.

The Best Supplements

If your pond lacks vegetation, I would highly recommend giving supplements to Koi as they boost their immune system.

Please note that these products cannot be substituted with their dietary staples and should be offered as occasional treats only.


Oranges are rich in Vitamin C, and so they are a powerful antioxidant that helps reduce the stress level. Cut them into small pieces and put them into the pond. After your Koi have finished munching on it, remove the remaining pieces from the pond. See the video below by KoiRun as an example.


Lettuce is an excellent source of minerals and vitamins for Koi. Just shred a few leaves of lettuce and let them float in the pond. After a few hours, remove the remnants of lettuce leaves to prevent water contamination.


Koi crave proteins, and prawns are high in proteins. However, they should be only fed in summers when Koi require a bit more protein than usual for extra energy.

Insects and Larvae

Koi adore insects and larvae in their diet. Consider offering the food with a healthy amount of insects and larvae to your Koi. Mealworms, crickets, blackworms, wax worms are well-suited supplements for Koi.


Koi Quantity

If you’re new to Koi keeping, it is highly advisable to not overcrowd your pond. Also, Koi don’t get along with other families of fish so well, so keep your Koi away from other fish to enjoy the beautiful sight of colors and non-stop swirls in your garden pond.

Koi love freedom in swimming, and they might get aggressive if the tank or pond is too overcrowded. For Koi pond fish, a pond size of over 1500 gallons of water and 3 to 4 feet deep in depth is ideal. Adult Koi can get very large.

Water Temperature

Koi is a cold-water fish, however, they thrive in water temperatures between 59-77 degrees Fahrenheit. During winters, when the water temperature falls below 50 to 41 degrees, you will need to feed your Koi twice or thrice weekly. However, when the water temperature falls below 41 degrees, stop feeding it altogether.

Water Quality

Another important factor that contributes to Koi fish care is maintaining water quality.

Keep in mind that impure water results in the death of Koi. Therefore, keep their pond water clean, aerated, and balanced. If you’re using tap water, make sure to add crystalline sodium thiosulfate to remove the traces of Chlorine. The pH level of the pond water in which Koi are kept should be 7 to 7.5. Anything below or above this figure is harmful to Koi’s health.

Water should be replaced by 20% through a water pump every week to ensure the best conditions.

Water filtrationis one aspect that cannot be neglected in order to keep your Koi pond active and healthy. Water filtration is done by two methods; 

Mechanical filtration: eliminates solid waste such as dried leaves, other plants, and insects.

Biological filtration: eliminates harmful chemical wastes, such as food and toxic wastes of Koi fish into harmless compounds.

Koi is an asset, and before you make an investment, I’d suggest you do your homework. Prepare the Koi pond, install the filters, netting, and give your new pet a very warm welcome.

There are several factors to maintaining water quality in your Koi pond.

Tips for buying the right filter for your pond

Aquascape Pond Skimmer

When buying a filter system for your Koi pool, we should consider a few things.

1. The filter system should carry out both the mechanisms, i.e. mechanical and biological. 

2. It is crucial to clean the mechanical filter daily to prevent the spread of bacteria and other diseases, so the filter should be low-maintenance to save you time and money.

For a filtration system, it is recommended to purchase a pond skimmer and mate it with a proper biological system. The skimmer will work on the water surface. If you work in a waterfall system, this will give you proper gas exchange and waterflow in your pond.

Managing Oxygen Levels

Koi needs Oxygen and proper gas exchange to carry out their body mechanisms, and they benefit the most from dissolved oxygen levels of around 8mg/liter in water temperature of around 77F. If you’re keeping aquatic plants in your Koi pond, know that you need to measure and maintain the oxygen levels as plants, including bacteria and algae inhale Oxygen and exhale Carbon dioxide at night, so there needs to be some form of aeration to keep your Koi healthy and thriving.

Fun Fact: Koi fish are the least active in cool waters, Increase oxygen for maximum activity

Tips to keep your pond properly oxygenated

Oxygen is the basic life necessity of all living creatures, and Koi are no different.

Here are some tips to keep your Koi pond properly oxygenated.

  1. Cool water carries more oxygen than warm water, so plan your Koi pond near shade trees or plant lily pads to keep the temperature down during hot summer days.
  2. Make the necessary oxygen level adjustments by regularly examining your pond water.
  3. Aeration equipment such as bubbling devices needs to be installed to boost Oxygen levels.
  4. Keep your Koi pond clean from dead matter (leaves, insects, waste) to prevent water contamination.

Ammonia, Nitrites, and Nitrates

API Pond Master Test Kit

Ammonia, nitrites, and nitrates are the evil trio for your Koi fish. The traces of these elements should be monitored closely to keep your Koi away from toxins and your water quality high. Let’s first talk about Ammonia.

  1. Ammonia: Ammonia, being the most toxic of them all, is the forbidden fruit for your Koi. That being said, when the Ammonia level reaches 0.25 ppm in your pond, the water deteriorates and has adverse effects on your Koi fish.

It’s best to test your water quality with a proper pond test kit. Check out our best aquarium test kit post for a list of recommendations to make sure you need your water conditions in top shape.

Symptoms of High Ammonia Levels

The ideal level of Ammonia in your Koi pond is 0.00 pm, parts per million. However, when a certain limit of Ammonia level is reached, Koi shows the following symptoms:

  1. Excessive slime or mucus secretion.
  2. Burns on fins and gills.
  3. Fins and skin redness.
  4. Clamped fins.
  5. Lack of physical activity.

How to remove Ammonia from your pond

When ammonia accumulates in your Koi fish pond, it’s your job as a responsible Koi owner to remove it from the pond.

Expert hobbyists recommend introducing beneficial bacteria to reduce the risk of Ammonia accumulation. Also, partial water changes promote good fish health and reduce high Ammonia levels in ponds.

Nitrites and nitrates

Nitrates and Nitrites are not as hazardous to Koi as Ammonia, but their traces in Koi pond can affect Koi’s liver, spleen, nervous system, and kidney. Nitrites and Nitrates mark the death of Koi if not removed timely. If you need to better your water quality and reduce nitrates – you can use media. Check our our Best Nitrate Remover post for recommendations.

Symptoms of high nitrates and nitrites in your pond

The ideal level of nitrates in Koi pond is 20-60ppm, parts per million. If the range exceeds 80ppm or more, you should be highly concerned.

The high level of nitrites in the Koi pond causes a condition known as brown-blood-disease. Brown-blood-disease prevents the Koi from absorbing vital oxygen from the water. This results in suffocation, which leads to fish mortality.

However, the safe level of nitrates in the Koi pond is 0.00 ppm. The accumulation of nitrates can cause damage to the veins, reproductive, and immune system.

How to remove Nitrites and Nitrates from your pond

Ammonia is broken down by the good bacteria into nitrites and nitrates. It is your job to further eliminate these toxic elements from your pond for the betterment of your Koi’s health.

Introduce more bacteria to the pond to keep your nitrites level balanced. Furthermore, increasing the aeration and partial water changes will help in getting rid of the evil trio completely.

Introducing aquatic plants to your pond

If you are someone who loves to charm their visitors, I’d highly recommend you adding plant life to your pond. Aquatic plants add opulence and improve Koi fish life. However, selecting the right aquatic plant and ensuring their ideal placement in the pond are bonus points to Koi fish care.

Advantages of introducing aquatic plants to your pond

Here’s why you should consider adding aquatic plants or water gardens to your Koi pond.

  1. Increases oxygen production.
  2. Improves aeration.
  3. Eliminates ammonia.
  4. Stabilize pH levels in your pond.
  5. Prevents the spread of algae by limiting the photosynthesis process.
  6. Provides natural filtration mechanism for your Koi pond.

Tips and tricks to introduce aquatic plants to your pond

Koi are voracious eaters, and they may end up eating your aquatic plants. Therefore, planning is the key before introducing plants to the Koi pond. Here are some tips and tricks to help your aquatic plants thrive in the Koi pond.

Vegetative Filter

Installing a vegetative filter is an ideal choice for you if you want your aquatic plants in a separate containment area that connects with the main Koi pond.

The best aquatic plants for veggie filters are:

  1. Water celery.
  2. Umbrella palm.
  3. Water Hyacinth.
  4. Sweet potato plant.

Plant Shelf

Installing plant shelves in your Koi pond is the best way to introduce aquatic plants to Koi pond. A plant shelf is any container with ideal water depths to keep your Koi safe from predators.

However, installing plant shelves might get a bit technical for “first time Koi keepers” as plants require water depth tailored to the needs of plant type.

For example,

Water lilies and oxygenators require a water depth from 12 to 36 inches of water.

Therefore, I don’t recommend installing plant shelves until and unless you’re an avid Koi keeper for the following two reasons:

  1. Predators like raccoons can use the plant shelves as a feeding ground.
  2. If your Koi is unwell, they might isolate themselves under the shelf away from your sight and eventually die.


Are They Easy To Maintain?

Koi fish can be easy to take care. However, they have specific challenges that make them not the best choice for beginners. They require a large pond and because their ponds are outdoors there are a number of issues to handle with cold winters and hot summers.

Are They Expensive To Maintain?

On average, a full size Koi Pond will cost around $3,000 per year. This makes them on average more expensive to keep than a dog or a cat. It is much cheaper to keep smaller fish in an aquarium indoors.

Do The Ponds Need A Heater?

In general, no. A Koi pond does not need a heater. They can tolerate a wild range of temperatures. If anything, you will need a pond de-icer in areas where bodies of water will freeze and shade to keep your koi pond cool in the summers.

Final Thoughts

Koi keeping is an incredible hobby, and it gets more exciting with each passing time. However, if you’re new and reluctant to domesticate Koi, I’ve shared the complete Koi fish guide for your reference. The tips and tricks mentioned in the article will help you outshine as a new Koi parent.


  1. I’ve always wanted to add an aquarium to my home office to help brighten up the place, so I have decided to get one where I’ll be raising koi fish soon. I appreciate you informing us that koi are prolific parents that reproduce thousands of eggs during their mating season, and since they grow rapidly too, they need a vast, warm habitat for them to stay healthy and happy. I’ll take note of this while I look for a pet store in the area that has koi fish for sale.


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