My name is Taro Kodama and when I first started working for my Koi Master father more than 20 years ago, one of the things that surprised me, was that we used salt so much. I mean A LOT of salt!

Some of you may have had a similar experience as mine in your koi research and wondered, “Is salt actually good for a koi pond?” or “Can I just use table salt (Morton salt) in my pond?”. 

To help our koi hobbyists have the healthiest pond for koi, I would like to discuss proper salt usage in this article.

Table of Contents – Salt in Koi Pond

• Is Salt Good for a Koi Pond?
• Why Do We Use Salt?
• How Do You Use Salt for Koi?
• What Type of Salt for Koi Pond?
• How Much Salt Do I Use in Koi Pond?
• How Do I Check Salt Level in My Koi Pond?
• Will Adding Salt Kill Pond Plants?
• How Can I Measure Pond Volume Using Salt?

Is Salt Good for a Koi Pond?

Yes, it has many benefits for creating a defense against bacteria and parasites.

When used correctly, it effectively treats new, stressed, or sick koi in your pond. If you want to use salt in your pond, then read through this article very carefully and ensure you understand how it is used before adding to your pond.

Too much salt is toxic and can even kill your koi, so be careful when you say “It is good for koi”. Salt is good for defending against bacteria; but in fact, it is actually harmful if used too much.

Why Do We Use Salt, Non-iodized salt, Sodium Chloride (NaCl)?

Salt will help to treat parasites, fight nitrite toxicity, and improve mucous slime coat production with an inexpensive solution that will fit in with your biological filter. Learn more about winter pond prep and survival in our blog post.

There are 2 main reasons why we use salt for Koi, both are about maintaining a healthier fish:

1. Use salt to take care of parasites and/or bacteria on a Koi’s body. Koi live in freshwater. So do parasites and bacteria. A koi pond salt treatment helps eliminate freshwater parasites and bacteria. I personally feel that parasites are becoming more resistant and that salt hardly kills parasites, but it still works well for something like columnaris bacteria.

2. Use salt to promote sickness recovery by balancing a Koi’s osmoregulation. To explain, a Koi is a freshwater fish; but because the salt level of its body fluid is much higher than the surrounding water, water keeps coming into its body. Its body does not burst because it can release water as urine and thus stay balanced. When a Koi gets sick or stressed, that affects its body’s function of balancing osmotic pressure. To help remedy this, we can add salt to raise the koi pond salt level to closely match that of a Koi’s body fluid. This way the water does not enter its body as much. The benefit is that the Koi’s body does not have to work as hard which helps the Koi recover quicker.

An extra advantage of salt is that it is not a medicine. So we don’t have to worry about any side effects.

What koi issues can salt help with? According to Dr. Erik Johnson, an author of “Koi Health and Disease: Salt at 0.3% is credited with the clearance of the following:

• Chilodinella (24-36 hours)
• Epistylis (24 hours irregardless of temp)
• Ichthyophthirius (72 hours at tropical temperatures)
• Costiasis (Ichthyobodo necatrix)
• Trichophrya (24 hours irregardless of temp)
• Glossatella (24 hours irregardless of temp), (24 hours regardless of temp)
• External Tetrahymena
• Almost every single Trichodiniid/Tripartiella organism.
• Inhibits trematode reproduction, clears 30% of adults.
• Inhibits Lerneiid reproduction

How Do You Use Salt for Koi Health?

Now that you know why salt is used, the next question is, “Should I put salt in my koi pond?”

There are 2 scenarios when we use salt:

• When your Koi swim awkwardly or are obviously sick.
• When you buy a new Koi and bring it to your home.

In both situations, it is highly recommended to treat the Koi in a quarantine tank with salt.

Before you add salt, remember to remove plants, clean the pond, and perform a 50% water change if you have time to delay the salt treatment.

In the winter and fall, some say that using pond salt will help survival during the cold winter months, but we do not agree and believe you should only use salt when it is needed. If you have a pond heater, then that will be enough to keep koi functioning through the winter. Always use salt in a quarantine tank or temporary tank to increase fish’s natural resistance to disease.

You may consider letting the salt dissolve in a bucket of pond water before you add directly in the pond, to keep it from burning koi with an area that is too concentrated or not yet dissolved.

Leave in the water and add in gradually. It may take 14–21 days to completely remove parasites, varying under different temperatures. Add the salt all at once if your fish are dying rapidly.

Remove salt with partial water changes. Don’t pour out the excess water onto a tree or plant since it could do some damage.

What Type of Salt for Koi Pond Salt Treatment?

Use non-iodized pure salt. You can buy a big bag of salt at a hardware store like Home Depot or Lowes.

Please never use salt with formalin. Salt and formalin do not get along. If you use salt and formalin together, it could kill your Koi. Regarding what kind of salt to use in your koi pond, avoid table salt and any iodized salt.

Salt is toxic to Koi if used at high levels for longer periods of time. If using too much, it will shut down their kidneys, and one of the reasons many people have Koi with “pop-eye” or symptoms like Dropsy.

How Much Salt Do I Use In Koi Pond?

The dosage varies from 0.3%–0.6% salt level for treating illness.

Otherwise for consistent use, 1 kg (2.2 lb) of salt per every 1000 liters (265 gallons) of water, which makes approximately a 0.1% salt water solution. 

I recommend you start with 0.3% and gradually raise it to 0.5% as needed. 0.6% is recommended only when your Koi seems to be very stressed or sick. Read more about helping sick koi in this blog article.

Spread out your salt treatment throughout a few days and continue monitoring the salinity levels. You DO NOT want to use too much salt for the safety of your koi, too much can be deadly!

Remember that salt does not evaporate; and when doing a water change, add your salt based on amount of the water replaced, not the total volume of pond.

Quick Salt Bath Option for Koi Rescue

(Be Careful!) – There is another way to use salt. It is a quick salt bath. You dissolve as much salt as possible in a bowl of water. Then, you move the Koi to the bowl and leave it there in the highly concentrated salt water for a short time.

This is mainly to kill any parasites or bacteria on the surface of the body. The Koi will start floating, and you will see a white layer developing on the body. Then you rescue the Koi from the bowl and release it to your pond. However, it could kill Koi if done incorrectly. So I will recommend this method only if you are with a professional dealer.

How Do I Check Salt Level in My Koi Pond?

Use a digital salt meter. Please never guess your pond’s salt level. I had an accident once before at my farm.

One experienced staff member had added a regular amount of salt in one of the tanks. But soon after, Koi started dying. At first, we did not know why; but found out later that there was some salt left in the tank from a previous use. She had not checked the salinity. She simply assumed that all the salt content was gone and added another regular dosage of salt. That addition increased the salinity much higher than the Koi could handle; and they died.

So please check your salt level every time before adding salt to your pond.

Will Adding Salt Kill Pond Plants?

If you have water plants, you are definitely now wondering, “Will salt kill my pond plants?” The answer is that many pond plants cannot take as much salt as your Koi. So if you are unsure if the plants can take salt or not, remove pond plants before you add salt to your koi pond. For this reason, I usually recommend you avoid growing water plants in Koi ponds.

As salinity level increases, these pond plants become less able to tolerate and are sensitive to salt:

• anacharis
• water hyacinths
• lotus
• lavender musk
• water lilies
• forget-me-nots
• zebra rush
• cattails
• floating hearts

Even with the ability to remove and control blanket weeds or algae, it is risky to use salt treatments with your pond plants.

How Can I Measure Pond Volume Using Salt?

We can also measure pond volume using salt. Surprisingly most Koi hobbyists and pond owners do not know their ponds’ volume. Here is a way to use salt to get a more exact amount of water volume.

Some owners may have the information; but a lot of times, it is simply a rough estimate. One time a client of mine believed he had a 10,000 gallon pond, but we found out that it was only 3,000 gallons. That really scared me because what if we had used medicine or salt based on the wrong information? It could have destroyed the whole population of his pond.   

If we use a salt concentration equation, it is pretty easy to calculate your pond’s exact water volume. Here are the steps:

1. Check the salt level of your pond with digital salt meter
2. Add 1 lb of salt or any appropriate pounds of salt
3. Recheck the salt level, ensuring that all salt is completely dissolved 
4. From the difference of the salt level’s new percentage, calculate the total water volume as follows:

If you use liters for pond volume, the formula is KG / % = VL.

• KG = kg of salt added
• % =  actual concentration change in %
• VL = Volume in liters

For example, you estimate that your pond holds about 10,000 liters (approximately 2,650 gallons). 

1. You check the salt level. From a previous use of salt, the reading shows 0.1%  
2. To increase another 0.1% in 10,000 liters pond, you must add 10 kg (approximately 22 lb) of salt. So you add 10 kg of it to your pond
3. After the salt completely dissolves, the reading now shows 0.18%
4. So 10 kg of salt increased the salt levels by 0.08% (= 0.18% − 0.1%).   10 / 0.08% = 12500. This means your pond holds 12,500 liters (approximately 3,300 gallons) 

If you use gallons for pond volume, P/(%*10) = VG

• P = pounds of salt added
• % =  actual concentration change in %
• VG = Volume in gallons 

Use this formula for the same example.  22 / (0.08 * 10) = 3300.