tratamiento de sal para koi

Salt for koi … the perfect remedy for any koi disease ?

Salt for koi appears to be a “natural” and “universal” remedy to treat any koi disease.

This at least many koi lover told us.

Like any product, salt has its advantages and disadvantages.

And it is not “universal” – it does NOT fit for everything.

Again – and I am aware that I repeat myself – I would like to emphasize an essential and basic issue: Before applying ANY remedy, you must find out the reason for the discomfort of the koi.

Aspirin will serve you when you have a hangover, but not if you have a headache because you banged your head against the door or because you have a tumor.

This article will explain how salt works and what for (and what not) it serves.

Starting from scratch: A koi is NOT a saltwater fish.

Salt is a traditional method used by breeders when there were still not special products for certain diseases. Due to this fact, there are bacteria that are already immune to salt treatment.

From breeders this traditional method has passed to koi dealers and now all koi fans think they have the perfect antidote to any discomfort.


Salt for koi … Why should you put salt in a koi pond ?

We start from the beginning: What causes the salt in the koi pond?

Do you remember the term “osmosis”? Maybe some do not know, others vaguely associate this word with the era of high school during “Physics and Chemistry” classes …

The simplest definition I found is: Osmosis is the spontaneous net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides.


salt for koi treatment in koi pond

Salt for koi: the process of osmosis

A container with a semipermeable membrane in the middle. One side with concentrated sugar solution and the other side with dilute sugar solution. 


The process of osmosis is that the liquid of lower concentration “goes” to the more concentrated liquid. In the case of the drawing, it would be from right to left. As sugar is too large it can not pass the membrane, so that the water particles have to go across to produce an isotonic (balanced) fluid.

The high concentration liquid is called hypertonic.

The low concentration liquid is called hypotonic.

A balanced liquid is called isotonic.

Why do I explain the term of osmosis when we talk about salt in the koi pond?

Because the koi is continuously doing osmosis:

  • Generally tap water has a salinity of 0.05%.
  • The koi usually has a salinity of 0.9% on its body.
  • And its body and gill represent the “semipermeable membrane.”

As the salinity of the koi is higher (0.9%) to the pond water (0.05%) the koi constantly works to reach the isotonic state.

If we add salt for koi to reach a salinity of 0.9% then the koi does not have to strive for osmosis. Less work for the koi – specifically to its kidneys. So it can use this energy in another way such as recovering from an illness.


If your koi are continually stressed, you must find out the cause (not enough oxygen, ammonia and other parameters of water imbalanced, poor filtration, too many koi etc.)

Adding salt to the whole pond should be the last choice you have left, because it is an awfully long process to remove salt.

The salt is not removed – the salt is diluted.

For a better comprehension, I leave you a table which shows this long process:

salt for koi tratamiento de sal para koi

Salt for koi: Dilution of salt after several 10% and 15% water changes

On the left side of the table the amount of salt shown in the water while carrying out constantly a change water of 10%. The last line shows that after 10 water changes of 10% there is still 34.87% of the added salt. The left side of the table shows the same calculations with 15% water change.

For this reason, as I said above, adding salt to the complete pond is something that should be very well thought (a total water change would be a too big contrast for the koi).

Another very important aspect to consider: Adding salt for koi is interpreted as an irritation against which the koi will produce more mucus. This mucus layer contains antibodies and protects them against parasites and therefore is considered positive. But … if the koi continues to consistently produce mucus – in excess – the gills  will be blocked (by the mucus) and less oxygen can enter the koi, which results in weakening the koi and thus salt becomes counter-productive method.

Salt for koi … where it really helps

Immune system

As we have seen, an increase of salinity is considered as an irritation, which the koi “answers” with increased production of mucus, which helps to protect. If it is a sporadic and short-lived remedy it is useful.


As explained above, the increased production of mucus helps to protect. If the parasite can reproduce quickly (because humans do not interfere with proper medication)  the koi can produce too much mucus, which is counter-productive (see above).

ATTENTION: parasites such as Trichodina and Costia reproduce more easily with salt !!! It is efficient against Chilodonella.

So again, if you do not know what parasite is attacking your koi (only the microscope can tell), adding salt presents a great danger.



Bacteria are a very sensitive issue. They are very difficult to see (only with electromicroscope and some only with contrasting liquid), difficult to define and more difficult to combat. If you do not know what you are up against, you should not add salt.

ATTENTION: let’s not forget that we also have bacteria in our filtration system. Therefore, if we kill with salt “bad bacteria” in our pond, also we kill “good bacteria” in our filter (with all the consequences).



Against virus there is not much to do. We can try to help to increase their self-defense, but most of the time we can not do more.



A large wound is a water inlet into the body of the koi. This means even more osmosis effort for the fish. Here salt can help. A quarantine pond with 0.9-1% salinity may be favorable for wound healing.



If you have a peak of ammonia (by too much food, too many koi etc.), salt can help increase the mucus and protect themselves from “burning” of ammonia.

ATTENTION: a CONSTANT increased value ammonia is toxic to koi and should not be remedied with CONSTANT salt.



Nitrites reduce the hemoglobin in the koi’s blood. Hemoglobin transports oxygen in the body. An increase of nitrite is extremely dangerous, because the koi can suffocate. The chlorite anions of the  salt compete with the anions of nitrite and neutralize the toxic effect. Here salt is an appropriate remedy (1 to 3 kg for 1000 liters of pond water).



Salt water damage the pigments and therefore fade the colors of your koi.


Salt and other products

There are very controversial discussions when it comes up to using salt in combination with other products such as permanganate, formalin and anesthetics.

Koi Hacienda always defends the process: First determine the cause of any discomfort and act on time with the right and specific product – not widely. For this reason we think it is better not to mix salt with any other product.


Salt for koi

Salt for koi: any kind of salt is appropriated – but without iodine

If you decide to apply salt for a particular koi with a salt bath, you should use 15 grams of salt per liter of water and bath the koi 10-15 minutes. If the koi begins to lose balance, take it out immediately and re-enter it in the pond. Remember that a salt bath for koi is an irritation – a lot of stress. Stay during this time with koi – do not go away. It may also be advantageous to cover the tank, so that the koi can not jump out.

Summing up: There are only two very specific situation for using salt:

  • when a koi has a large wound => salt bath in a quarantine tank
  • when nitrite values are alarming

In other cases, salt has few or even reverse effects.

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Salt dilution: