An introduction to Fujio Oomo and Tamikazu Kobayashi’s article by Tony McCann

Salt is often considered to be the koi keepers greatest ally although it should be remembered that it is a chemical albeit naturally occurring and that koi are freshwater fish and not saltwater fish. Salt has been used for short term bathing or dips, medium term as described in the following article and as an additive during winter. I personally would not put salt in a pond unless the circumstances require it as outlined in Fujio’s article.

What I find particularly interesting in the article are the descriptions of “the loss of condition” which led me to think of how many times do koi keepers see signs of fish losing condition or looking unhealthy and the first thing they do is reach for Potassium or Formalin and Malachite. Could the 0.5% concentration of salt be the answer in many of these situations and assist the fish back to health without the harsher treatments previously advocated? It may seem, particularly for those with large ponds, quite radical to tip many kilos of salt into the water but if it reinvigorates the koi’s health then it could well be worth it.

Fujio described two occurrences to me which happened to koi that he was growing in concrete ponds within their main greenhouse, something which is closer to our style of koi pond than mud pond growing. One situation was where a number of fish were moved from one pond to another in the same greenhouse and after moving exhibited signs of stress or as he terms it “they lost condition”. The second situation was upon his return from a foreign trip he inspected all the ponds and in one pond the fish were again looking unhealthy with a mucus deposit and one of his colleagues immediately ran for the Formalin and Malachite believing it to be parasites. This was probably a water quality problem as a result of the high feeding level. Both situations were instead dealt with by bringing the salt level to between 0.5% and 0.6% (approx. ⅘ per ounce per gallon) and both groups of fish recovered their condition within 3 or 4 days. One further point which Fujio made when we discussed this issue was that he believes that a collection of fish must be treated in accordance with the condition of the weakest fish so that if there are one or two fish in a pond showing signs of concern then the treatment should be applied to the pond as required by those fish and not treated separately.

I decided to do a little bit more research and to explain some of the technical issues in Fujio’s article and found some very interesting items contained within two manual on fish health, both written in the 80’ but both by highly respected scientifically qualified persons, one Dr. Chris Andrews from the UK and the second by Dr. George Post probably the author of the most comprehensive text book on fish health. A quote from Dr. Andrews “Stress is a vital factor in fish health. Factors that have a negative impact on fish are handling, overcrowding, poor environmental conditions and the stress response which is caused involves the release of hormones that channel the fish’s energy and can cause long term detrimental effects, ie loss of condition. One of the hormones released is adrenalin which disturbs the osmoregulation within the koi.”

Dr. Post writes “The most common diseases of fish related to physical factors are associated with osmotic pressure, environmental temperature, Ph, dissolved air and mechanical trauma.”

Dr. Andrews tells us that “the body fluid of freshwater fish (ie koi) has a higher concentration of salt than the surrounding environment. The tendency therefore is to for water to flow in and salt to be lost from the tissues. To counteract this they have very efficient kidneys which excrete water very rapidly, salt is minimised by efficient re-absorption of salt from urine before it is excreted.” When these processes are out of balance due to the effects of stress or loss of condition then the addition of salt in a manner described in Fujio Oomo’s article helps redress the balance and assist the fish to recover from the effects of stress. In simple terms it will regain its good condition.

I can think of nothing more stressful to koi than being transported in a polythene bag for as much as 40 hours which occurs when koi are shipped from Japan to the UK. When I take delivery of such a shipment they are placed in water containing 0.5% salt per gallon. This concentration is maintained until all signs of stress have disappeared and then water changes will slowly dilute it. Within 10 days of my last shipment which arrived in November a Cefas representative who was carrying out his annual inspection of our ponds remarked upon their excellent condition. I therefore wholeheartedly support Fujio Oomo’s recommendations.

Why the Salt bathing works so well when Koi loses condition?
(Understanding your fish's health)

Nishikigoi Niigata Direct, Ltd.
Executive Director: Fujio Oomo
Director: Tamikazu Kobayashi

Salt bathing has been widely known and done among Nishikigoi breeders as a practice, when koi loses condition, being harvested, or moved from one pond to another. But is this just based on experiences? Is there some back ground that salt bathing is really useful and effective? Is salt bathing merely a superstition?

We'd like to bring some light into few points that salt bathing helps koi to recover from a suffering condition. Before taking up the main subject, I had better explain the “the word, salt bath” which has two meaning.

1. Salt bath for 10-15 days

2. Quick salt bath for 3-5 minutes.

In this article, when we say “Salt bath or Salt bathing”, please understand it means “Salt bath for 10-15 days”

< First aid > (What comes “first”?)
First aid comes in importance when your koi are apparently in suffering condition. Let's see, in human, the universal steps in first aid are;
• Checking consciousness (and securing air way)
• Checking voluntary breathing
• Checking heartbeats...
Of course, if your koi is lying down on the bottom of the pond, it could be too late to do anything, and it is difficult to look for vital signs on your fish, but checking and securing air way is considered to be the most basic step in first aid. And necessary treatments are done (such as respiratory aid, drip infusion, blood transfusion in order to stabilize the patient's vital signs, ever before further treatments or operation is done. We can learn from this when helping fish to recover from a difficult condition.

<Salt bathing and osmoregulation*(1)>
Causes and symptoms of koi in difficult conditions
There are a few patterns of causes which koi lose condition.
1. By parasite – (koi produce more mucous cells, gills get clogged and osmoregulation becomes difficult.)
2. By stress and sudden changes of environment. - (koi produce more mucous cells, gills get clogged and osmoregulation becomes difficult.)
3. By indigestion. - (koi loses body fluid and body minerals then osmoregulation becomes difficult.)
4. Or any of these above combined.
As you notice, all of these causes are closely related to the downturn or the hardness of osmoregulation

Let us proceed to some symptoms you can find by making close observations
・Slow movement
・Clamped fins
・Staying at a same place
・Gather around a place new water comes in
・Rapid gill plate movement (breathing action)
・Pinkish skin and more mucous coating
・Fins look thicker and dull (not transparent)
・Sunken eyeballs
・Loss of mucous coating
・Koi loses balance and lays down
・External and internal bleeding

*(1) osmoregulation -
Look up osmoregulation in Wiktionary, the free dictionary. Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too
diluted or too concentrated.

<Two very important organs to sustain fish's life in freshwater>
Gills and kidney are the organs which play the most important roles in sustaining fish's life in dealing with osmotic pressure.

Take in oxygen and put out CO2
Discharge ammonium
Take in sodium (Na+) ion, kalium (K+) ion and other minerals

Filters important body minerals and keeps them in the system
Takes out water from the system and put it out of the system

<Dealing with osmotic pressure>
Freshwater fish are constantly exposed to the dangers of water soaking into body cells and losing their body minerals, because of osmotic pressure difference between fish body and freshwater. Just a quick explanation about osmotic pressure – when you have salt-preserved vegetable, and you put it in freshwater, the vegetable absorbs water, and sodium comes out of the vegetable. This is done by osmotic pressure. Water moves from low osmotic pressure to high osmotic pressure. It is said that freshwater fish use 30% of their basal metabolism to keep their body minerals in and to keep water
out of their system. Let's compare this to human system – humans use 39% of the basal metabolism in skeletal muscles in order to keep body heat in level. Fish do not need to keep their body heat in level. But it is important for fish to control osmotic pressure – to keep too much water out of the system and to keep necessary body minerals in the system. So you can see how important it is for fish to maintain osmoregulation system in order. This is a tremendous amount of energy for them.

<Salt bathing and osmotic pressure>
In humans, when you have diarrhea and dehydration from it, you'd get a treatment for it – most times, a drip infusion of physiological saline solution. You'd need to do the same thing with koi. In case of freshwater fish, you put them to 0.5-0.6% salt bath for 10-15 days. If freshwater fish lose condition, it becomes difficult for the fish to sustain osmotic pressure control. Then water comes into the system and body cells get swollen. Especially, when gill cells are swollen, it becomes difficult for fish to do gas exchanges and discharge ammonium from its cell surfaces. This brings the fish a lack of oxygen and ammonia intoxication from its own body waste in the blood. So, putting fish to a salt bath (for 10-15 days depends on its condition) helps fish to “breathe” normally and discharge ammonium, and at the same time, it also helps fish to keep water out of its body circulation system, because there(0.5-0.6% salty water) is not much difference in osmotic pressure between the fish body and the surrounding water. And this also helps fish to save a lot of energy, because fish doesn't need so much energy to run osmoregulation system.

So salt bathing( for10-15 days) helps koi to regain condition. It helps koi to take out excess water
from swollen cells and helps koi to breathe easily, it also helps koi from losing much energy when
they are in difficult conditions.

In the end after koi is coming back to normal condition after adjusting its body systems to new circumstances, it is no more necessarily to koi in 0.5% salty water, just try to get rid of salt level lower little by little by adding new fresh water to reach to 0 % of salinity level.

We hope that this article helps all of the koi hobbyists and dealers to understand your koi's health better and do hoping you can enjoy koi keeping much more.

Nishikigoi Niigata Direct Ltd. Fujio Oomo ( Professional expert for Breeding Koi) Tamikazu Kobayashi (Professional expert for Breeding Koi)
Sources: “Functional and morphological studies on fish's ion and osmoregulation in fish” by Toyoji Kaneko from Japanese society of fisheries science journal vol. 72 pp. 632-635 (2006)
“The Koi Doctor” © Maarten Lammens, A-Publishing /KINDAI bvba 2004
“Nishikigoi Mondo” © Satoru Hoshino and others, Shin Nippon Kyouiku Tosho Co., Ltd. 2007
and “Wikipedia”