build a fish pond

You are here: Home > Koi Health & Wellness Center

Koi Health & Wellness Center

Stress in your Koi

Stress is the term used to describe the sum of the physiological changes an organism incurs in response to adverse external influences. Those external influences are called stressors and include such things as injury, illness, environmental contamination, fear, medications, nutritional deficiency, overcrowding, parasitism, predation, reproduction, temperature extremes, transportation, or other similar factors. In many instances, more than one stressor is present at the same time.

The stress response in most vertebrate animals is to increase the release of endogenous catecholamines (epinephrine, or adrenaline) and cortisol from the adrenal glands, or in fish, interrenal tissue. This in turn stimulates a release of glucose (gluconeogenesis) by the liver. The blood glucose level elevates, providing more energy for a flight response or immune system response. The blood also shows neutrophilia (increased neutrophils) and lymphopenia (decreased lymphocytes). While causing an initial increase in protection, long-term effects of stress are a decrease in immune response (decreased antibody production and reduced phagocytosis ability) and therefore a decreased resistance to disease.

The Health of your Koi is almost always an issue of Water Quality, Koi husbandry and Stress. Most Koi parasites and diseases are already present in every Koi pond, your Koi have a unique system, in that, it already has in place what it needs to protect itself from most of these parasites. But when your Koi become stressed this unique system breaks down, and your fish and Koi become extremely susceptible to infectious diseases. Of course there are exceptions, but if you maintain optimal water quality conditions and know your fish's behavior you can prevent more diseases and save your fish's lives by helping them stay stress free.

Fish are made VULNERABLE to bacterial infections by water quality, crowding, wintertime chillling, infrequent pond cleaning, and parasites - and these issues have to be corrected before any success with the bacterial issues are possible.

What is "Aeromonas Alley"?

The following is the process your Koi go through after being introduced to a stressor:

Resistance — Catecholamine (the process of the body releasing epinephrine and dopamine). This usually takes effects in seconds or minutes. Fish attempts to regain "original" level of their psychological system or homeostasis.

Adaptation — Cortisol release. This usually takes effects in hours, weeks or months. Fish attempts to develop a new level of homeostasis under the influence of a chronic stressor.

Exhaustion — Fish exhausts its reserve of energy, hormone precursors which were needed to maintain the new psychological system.

Fish Medicine for Sick Fish and Koi

One of the main keys to Koi health is noticing what is normal behavior for your Koi. This way you will notice when they deviate from their normal behavior, which is the quickest way to tell when something is wrong or if they are under stress. Another major key to successful Koi Health is a routine examination of your fish. Check out your Koi and give them a good look over to make sure you don't see any signs of distress.

The more intimately we know the behavior of our Koi, the more reliably we can use our observations to gain a broad understanding of their state of health. As the health of our Koi is largely dependent on the quality of their environment, we can soon gather useful information about the quality of our water simply by observing our Koi.

Signs to look for:

Fins are often the first body part to deteriorate when fish are stressed or unwell so they can give a good general guide to condition. Examine all fins, especially those underneath the fish, for ragged or uneven edges, tears, splits or bloodshot appearance. Invariably, these conditions indicate a bacterial or environmental problem needing urgent attention and do not result from fish ‘nipping’ each other.

Check for any thickening of the mucous layer or cuticle, especially around the head and upper body surfaces, giving a milky or grey appearance to the skin. This could indicate a parasite problem.

Look closely for any reddening of the skin, abrasions or open wounds, particularly at the base of the fins, around the mouth and on the underside of the body. This type of damage often indicates a bacterial infection and only rarely results from bumping into rocks, pipes etc.

Some parasites you are able to see without a microscope so watch closely for these. Under the descriptions below of Koi & fish diseases it will tell you what you should be on the look out for.

Some of the most common bacterial infections that are associated with stressful conditions in freshwater systems are Aeromonas hydrophila, A sobria, and Pseudomonas spp. These opportunistic organisms frequently cause disease in freshwater fish, usually under warm water conditions. They produce very similar clinical syndromes, sometimes referred to as hemorrhagic septicemia. Nutritional deficiencies, traumatic injuries, parasitism, and sharp seasonal temperature changes appear to be predisposing factors.

The acute form is characterized by signs of a septicemic infection (blood poisoning) with external reddening, and hemorrhages are found in the lining of the abdominal cavity, body wall, and internal organs. Control is based on removal of predisposing factors.

Actions for Disease Control


Stress control

Never overpopulate or exceed the filtration capacity.

Immunization procedures: Certain vaccines are in use in some fish food for selected viruses, including CCVD, IHN, and VHS. Bacterins for prevention of diseases including Furunculosis and Vibriosis are also in use. Other vaccines are in the stage of research and development.

Probiotics are a great way to increase the health of your Koi naturally. One type of probiotic is KoiZyme. You can never eliminate the bad bacteria, but you can drive down the numbers to a point where they are able to handle those natural numbers and stay healthy. This is where the Probiotics come in, Koizyme are one of the types of pro biotic bacteria, which are simply a good bug which grows very quickly in your pond and takes up space in the pond. It's called a competitive exclusion. Koizyme bacteria grow faster than the bad bacteria, and it takes up space. The good bacteria will eat up the food that the bad bacteria need to survive, thereby eliminating the numbers of bad bacteria.

Coupled with a good environment, filtration, nutrition, and parasite control, products like KoiZyme are another great tool to give you an edge in making a truly healthy environment, which is a natural disease control.


When treating you need to have patience. You have to treat early but you also have to give time between treatments to allow the medicine to dissipate or break down before adding another dose. Another way to do that is to make small water changes between doses.

You need to treat according to the temperature of your pond. Most medicines are temperature dependent in how they work. Even the parasites themselves are temperature dependent. When the water is cold the parasite has a slow life cycle. With warm water, the parasite has a faster life cycle.

For Diseases Click Here

Anchor Worm Red pimples that develop into whitish protrusions that look like 1/2 inch splinters Aqua Prazi & Medicated Food or ProForm LA or MinnFinn
Dropsy Fish become bloated and scales stick straight out, giving them a "pine cone" appearance. Isolation tank with warm water (70°F - 75°F), add Minn-Finn.
Fin/Mouth Rot Deterioration of fins from the outer edges in, and/or deterioration of the membrane surrounding the mouth. Tricide Neo is also used for Ulcers or Minn-Finn can be used.
Flukes Flukes or Monogeneans are tiny, often microscopic and are one of the main causes of ulcers. Aqua Prazi or Prazi Pond Plus
Fish Fungus White coating or cottony fuzz on body and fins, may be greenish in color (algae). ProForm C or Minn-Finn
Gill Disease Sunken eyes, listnessness, gasping for oxygen. Isoloate, salt (1 lb per 25 gal) plus MinnFinn
Ich Fish scratch against objects, white spots appear, eyes become cloudy Minn-Finn
Oxygen Deprivation Gasp at surface, stay by waterfall in a.m., loss of appetite
Pop Eye Eye(s) become inflamed and reddish in color Isolate, salt
Trichodina Younger Koi (under one year) will show symptoms very quickly while Koi aged two years and more may not show any adverse signs until the infestation levels become much higher. Flicking and rubbing as they try to relieve the irritation caused by these parasites. ProForm C or Minn-Finn
Costia Koi have difficulty in breathing, slow erratic gill movements, they spend time near airstones and water returns, & they may be seen to rub and flick against the side of the pond. ProForm C, Chloramine-T or Minn-Finn

Most Common Reasons Koi Die

Ways to improve your water quality are:

  • Adding a dechlorinator to your pond when you add water.
  • Don't leave the hose on when filling your pond. Use a timer, or an automatic filler.
  • Have the right filtration unit for the size of your pond and the number of Koi you have.
  • * Adding aeration in you pond.

*Koi need a lot of oxygen. If you want to maintain the super quality of the colors on your Koi, you have to maintain a very good aeration supply. If your fish suffers in any way from lack of aeration, his colors will actually go down and diminish. Air, chloramines, and power outages are critical in keeping your Koi healthy.

Viruses and Bacteria:


These microorganisms cannot be seen with the naked eye. They cause many diseases in fish. Symptoms include: swollen, fluid-filled body cavity, bulging eyes, bloody fins, bloody spots on the skin or base of scales, sores, and lesions, etc. Bacterial infections are usually the result of a stress on the fish or infection of a wound.

Viruses are extremely small. They can only live and reproduce by invading a living cell within a living creature. Having said this, viruses can also be very resistant to extreme temperatures and adverse conditions, and can survive outside that chosen host for extended periods of time. This makes treatment of viral infections very hard, as treatment leads to the affected cells, as well as the virus, being killed.

The most effective way to combat viral infections is through vaccination to protect against infection, when a vaccine is available. The only other approach is to provide optimum living conditions for the fish and allow their natural immune system to overcome the infection.

Some viruses can remain dormant in Koi for months or even years, only becoming active again when the fish become stressed.


Bacteria come in many different shapes and sizes, but all are microscopic in size, and are single-celled organisms consisting of an outer cell wall which allows liquid and fluid to pass through. This is how they obtain nutrients.

Most bacteria reproduce by a process of binary fission, one become two - two become four - and so on. This process can happen very quickly which means that extremely large populations of bacteria can appear in a very short space of time, as long as a viable food source is available.

Bacteria are naturally present in a pond and they will survive in most conditions. In fact your Koi will live alongside the bacteria present in your pond quite happily until the environment conditions become less favorable causing them to become stressed and so susceptible to infection. Alternatively if any areas on your Koi become weakened-such as after a parasite infection or if physical damage has occurred-they will be attractive sites for the bacteria to attack.

Many bacterial infections can be treated via topical treatment, the use of a medicated bath, or even a pond treatment. However, in very severe cases antibiotics may be required but this should only be as a last resort, and advice should be sought from a vet or a local Koi specialist beforehand.

Remember, not all bacteria are bad; in fact the filtration system at the heart of your pond works because beneficial bacteria convert ammonia to nitrite, and then nitrite to nitrate and nitrogen gas.

Koi can be infected with bacteria that will also infect humans. Of particular concern are Mycobacteria which cause Tuberculosis in humans.

Most bacteria that affect Koi are able to live under widely different environmental conditions (especially either aerobically or anaerobically). But even the obligate parasites seem to be able to live a long time off the host. There are various modes of transmission which include passage through water to fish, fish to fish contact, or transmission from a vector (including humans) that carries the organism from one body of water to another. A portal of entry into the target fish is the next step in the process. The bacterium must pass through epithelial membranes in the skin, gills or gastrointestinal tract. An injury or a protozoan parasite can create such a portal of entry for the bacteria and enable infection. An infection or symptoms of a disease does not necessarily follow. A bacterial pathogen can be present in a fish and due to the lack of irritation of the bacteria or the fish’s immune system ability to fight it can stop the progression of this disease process. The bacteria must cause injury to the structure or function of tissue for a disease to result.

Fish Fungi:

Fungi multiply via spores. Some species of fungus can reproduce asexually (without the need for both a male or a female to be present) while other require both sexes to be present.

Many single-celled fungi can only be seen with a microscope, although others can easily be seen once they have reached an advanced stage of development. Common fungi include yeast, rust, mold and mushrooms.

Not all fungi are bad, and in fact some help in breaking down organic waste and keeping the natural balance constant.

Typical fungal infection in a Koi pond is characterized by the presence of fluffy white tufts, similar to cotton wool, which will appear in areas which are susceptible to infection, sites of skin damage, or places weakened by other infections. Fungi rarely attack Koi that are healthy, uninjured and unstressed.


These are microscopic, single-cell animals. They can be found on the gills, body surface or imbedded in the flesh. There are many different protozoans, and they cause a variety of fish diseases.

You are here: Home > Koi Health & Wellness Center

Keep Current With The Build A Fish Pond Blog

The Only Koi Book You Will Ever Need!

Whether you are a beginner or a Koi pond specialist this ebook contains all you need to know to have a beautiful, optimal ecosystem, with healthy pond fish!

~Price $20.00

Pay with Safe and Secure Pay Pal.


After Check out you will be taken to a page to download your Ebook.

The Importance of Quarantine

A Portland koi hobbyist paid $10,000 for an exotic fish and put it in his pond, only to lose more than $100,000 worth of fish because of a disease carried by the new acquisition.

If he would have put this Koi through a Quarantine process this would never have happened.


Inside the Koi is a gas-filled sac, known as the "swimbladder", which acts as a buoyancy organ so Koi can stay at any depth with the minimum use of energy. Koi can control the gases inside it, with gas added or removed by blood vessels running over the surface of it. There is also a thin tube to the Koi’s throat so they can add gas by gulping air.

There are various conditions that can affect the swimbladder, from fungus to filling with fluid. The symptoms are similar: they swim with a distinct rowing action and rise to the surface often to gulp air. When resting, fish are found on the pond bottom with the pectoral fins extended. Unfortunately, it is very difficult to determine what disease is affecting the swimbladder. Fluid can be removed, but without knowing why this has happened or how to control it, the swimbladder will fill with fluid again very quickly.


  • Barbel These act like taste buds.
  • Brain Set just above and behind the eyes, which provide Koi with excellent vision, the brain runs all bodily processes.
  • Gills Through these, carbon dioxide is releasd into the water and oxygen is collected by red blood cells. The gill tissue sheds ammonia.
  • Heart The three chambers (atrium, ventricle and sinus venosus) pump deoxygenated blood to the gills.
  • Liver This large organ stores food for distribution to the tissues. It breaks down unwanted proteins into ammonia, forms bile from old or nonfunctioning red blood cells and breaks down toxins and poisons.
  • Spleen This stores immature red blood cells and produces cells of the immune system.
  • Intestine Food is digested here (Koi have no stomach), by enzymes, and nourishes the blood supply.
  • Swimbladder Sound waves are processed here, then linked to the inner ear, enabling them to hear.
  • Gonads These sex glands are situated on either side of the body.
  • Vent Urine, excrement, eggs and sperm (milt) are all released here.

Immune System

The immune system is a protective mechanism developed by animals for survival.

Fish are one of the most primitive vertebrates, but they do have an immune system satisfactory enough to react and protect them from attacks by various organisms. The host-pathogen relationship usually elicits a response in the host (fish) which serves to protect it against the pathogen.

There are two types of immune responses elicited by most animals. A humoral response and a cellular response.

The humoral response is the stimulation of serum protein molecular synthesis homologous specific to the antigen causing the synthesis. These serum protein molecules are called antibodies. Antibodies circulate throughout the body. All potential pathogens contain antigens. The introduction of antigens by a pathogen is what stimulates the antibody response of the host.

The cellular response to antigen stimulation is a sensitization of cellular elements of the reticuloendothelial system.

Cardiovascular System

The heart circulates blood through a system of arteries and veins. Blood passing through the gills is oxygenated before being sent on to the tissues.

As there is no division between oxygen rich arterial blood and oxygen depleted venous blood, the Koi’s “primitive” cardiovascular system makes these fish vulnerable to low oxygen saturation levels.

What are those little red worms in your filter material? They are the larvae of the midge fly and are called Blood Worms, they are harmless. They are also a fish delicacy and can be purchased at your local pet supply stores. They are a natural occurrence in a clean pond.

Enjoy This Site?
Then why not use the button below, to add us to your favorite bookmarking service?

RSS Feeds


The danger signs of too little aeration are:

  • Your fish hover below the water return.
  • They gulp at the surface of the water.
  • You wake up in the morning and all your fish are dead.

The ways to increase the amount of oxygen are:

  • Add a "spitter" or fountain to move the water.
  • Add an aeration stone.
  • Add a Waterfall.

Try to keep all areas of your water moving.

Lateral Line System

The lateral line system is a special sense organ which provides your fish information about their surroundings. The lateral line system is what prevents your fish from bumping into things in the pond.

The lateral line system is a batch of small sensory patches underneath the scales on the skin. They can be seen as a line of small pores that run down the sides of a fish from head to tail. These pores are not confined to the lateral-line, they are also distributed all over the fish, particularly on the head.

Some sensory pores serve to detect pressure changes within the pond water. Fish set up their own pressure wave in front of themselves in the water so when they get close to something the pressure waves become distorted, these changes are detected by the lateral line system, which enable the fish to make the fundamental correction in their direction.

Taste Buds and Hearing

Koi have taste buds almost everywhere on their bodies. They have taste buds, on their lips, within their mouths, their fleshy barbells, and even their fins and tail are covered with taste buds.

Koi are unique in that they can hear up to 3,000 hertz, while most other fish cannot hear frequencies above 1,000 hertz. This is due to a unique amplification system they have which connects their inner ear bones to the swim bladder. This connection to the swim bladder greatly improves their ability to hear, as well as assists in balance and orientation.

Contact Us

PayPal Acceptance Mark

Return to top
Copyright© 2008-2030.Koi-Pond-Guide.com