Koi Health Ailments for Care for your Koi along with Koi Treatment
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Koi Health Ailments

Koi Health Ailments can be prevented and the 2 major prevention methods are: keep clean water and quarantine all new fish.

Japanese Koi fish are hardy fish, possibly only goldfish can compare with them. You need to be gentle with Japanese Koi fish, especially if you want to see them at their biggest and best. If your Koi becomes sick not only do you need to treat them but the source as well (the pond water).

One of the major problems of treatment of health ailments is that of diagnosing the condition.

Parasites are a real pond health issue when it comes to Koi Japanese fish. The most common way Koi Japanese fish contact parasites is from other fish. Before a new Koi is introduced to the pond, it is extremely important that the new fish be quarantined for 3 weeks. During this time period they should be treated for parasites. Isolating a Koi for 3 weeks in a quarantine tank, without Koi treatment, there is no assurance that they will be parasite free. All that tells you is that if it has parasites, there are not enough of them to make it sick at this time.

Parasites are creatures which require a host (your Koi) in order to eat, reproduce, and survive. This host may be needed for long periods of time, as is the case with some parasitic infections, while others may only need a host for a limited time for a specific event, such as reproduction.

Numerous common external gill, skin and fin parasites afflict Koi. Many of these are protozoans, such as Ichthyophthirius multifiliis ("Ich") or Ichthyobodo necator (“Costia”), and can cause significant health problems. Most of these parasites can complete their entire life cycles on the koi. The helminths (worms) are a broad group of parasites that include the skin and gill flukes (monogeneans), cestodes (tapeworms), nematodes (roundworms), and trematodes (true flukes). Crustacean parasites like Lernea (anchor worms) and Argulus (fish lice) are relatively common but don’t pose the acute mortality threat that some of the protozoans do. Ectoparasitic infections generally are more common and serious than internal parasitic infections. Your veterinarian can confirm a parasitic problem and recommend an appropriate therapy.

The following signs might indicate a significant parasitic infection:

  • Fish with discrete white spots, especially evident on the fins.
  • Fish with visible streamerlike “hairs” or “crawling” black spots.
  • Anorexia
  • Fish gasping at the surface.
  • Fish lying on the bottom of the pond.
  • Discolored fish (generalized pink to even red).
  • Fish appear opaque or covered by a layer of mucus.
  • Fish appear thin and sluggish, despite eating well.


Tricide-Neo is a patented dip to aid in the treatment of topical baterial infections such as ulcer disease, fin rot, tail rot and mouth rot. Fish can be dipped every other day for one week. The fish are dipped into the bath for 3 to 7 minutes -- that's fast !!

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Viruses can only be seen using a very powerful electron microscope. They can only live and reproduce by invading a living cell within a living creature. Viruses can also be very resistant to extreme temperatures and adverse conditions, and can survive outside the chosen host for extended periods of time.

One Virus that is deadly to your Koi and extremely contagious, but does not have a cure, is the Koi Herpes Virus (KHV).



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 becomes four-and so on. This process can happen very quickly. 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. Or if any area 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. If they have physical damage you could use Providone Iodine ointment.

If you start using KoiZyme in your Pond you will not have to worry about your Koi getting sick. This is the safest way to make sure you Koi and Pond Fish stay healthy.

Clinical signs of bacterial infection include:

  • Ulcers or visible defects anywhere on the body or fins.
  • Red spots or hemorrhage on the body or fins.
  • Anorexia
  • Fish gasping at the surface.
  • Fish lying on the bottom of the pond.
  • Bulging eyes (exophthalmia)

If your koi have large sores on their bodies and are rapidly dying they have either Aeromonas bacteria or Pseudomonas Bacteria.

The best product to use for bacterial infections is Tricide-neo, this product is as good as an injection.

Apiosoma (Parasitic Gill Disease)

Apiosoma is an external parasite which will attack the gills, skin and fins of Koi. If their numbers are allowed to escalate, they can result in fish losses. Apiosoma are ciliated protozoa, and are vase-shaped when viewed under a microscope. They have a large number of tiny hair-like parts which are used for controlling movement and in some cases even for feeding, these are known as cilia. These cilia are located in a circular arrangement at one end of the body. Apiosoma are very similar to Trichodina and Chilodonella and so many of the symptoms of this disease are similar to those infections. Thus a skin scrape must be taken and examined under a microscope for an exact identification to be made in order for correct treatment.


Less severe cases of the Koi Disease Apiosoma can easily be treated with a proprietary anti-parasite fish meds or the use of malachite green and formalin, the dose rate will depend upon the concentration of the mix. Pond salt can also be used as an effective treatment as either a bath or a pond treatment. If the infection has become severe, the chances are that there will be numerous sites of secondary infection on the fish and these will need a topical treatment such as propolis.

An effective Koi treatment against Apiosoma and other Parasitic Diseases is KoiZyme.

Bacterial infection in a pond can be caused by numerous species of bacteria, but the most common is Aeromonas hydrophila. This is found in nearly all Koi ponds, but as long as your Koi are in good health, infection will generally not occur. It is only when your Koi are stressed because of temperature fluctuation, overcrowding, poor water quality and other factors which have the effect of stressing the fish that the bacteria present can develop into a problem. If identified early, bacterial infections can be treated with the use of bactericides, but it is vital that it is caught early as advanced stages of infection may prove very difficult to treat.


The first course of action must be to take a swab from a Koi showing symptoms. This has to be sent away for processing. The result will give you all the information required to treat the infection, as the exact bacterium will be known, plus which anti-bacterial will be effective against it.

Symptoms of Aeromonas hydrophila include buildup of excessive mucus, and areas of reddening on the body which ultimately result in lifting of the scales which in turn may result in the presence of ulcers. In some cases the scale lifting does not confine itself to a specific location on the body and the infected Koi may take on a pine-cone appearance.

Dropsy could then develop as well as other conditions such as pop-eye. Internal problems may also be developing along with external symptoms. If losses do occur, internal examination may well indicate hemorrhagic septicemia around the internal organs which is identified by a reddening of these plus the presence of excess amounts of fluids and blood.


The best way to prevent bacterial outbreaks is to run a clean pond. It is impossible to eliminate bacteria completely from the water, so it is vital to ensure that the environment in which your Koi live is kept to the highest standard to ensure that levels of stress are kept to a minimum. This can be achieved by keeping stocking levels to a minimum, using your quarantine tank for new Koi, and maintaining constant water temperatures without fluctuations.

An effective way to keep your pond running clean is to use KoiZyme.

Using UV Sterilizers, these differ from the typical UV clarifier used by most Koi keepers in that they are not designed simply to stop green water, but work by exposing the pond water to a much higher concentration of UV light in order to kill waterborne pathogens.

Velvet Disease

This appears as a mass of yellowish white dots on the body and fins. The emaciated fish, especially if young, will die unless treatment is prompt.

The most effective medication for the treatment of Velvet is the substance called acriflavine, also called trypaflavine. The cures against Ichthyophthirius are somewhat effective but should be used longer than for the treatment of ich. As there is a chloroplast in the organism some prescribe to covering the tank completely to shut out all light while treating, thereby denying the free swimming stage a source of energy while it seeks a host.

A problem is that in young fry the treatment may be as fatal as the disease. Once mature, the organism falls from the fish to the pond floor where it develops a protective cyst. Within this, it multiplies and then the cyst bursts to release more parasites to infect the fish. If the free swimming forms do not find a host within 24 hours they die, but the cysts are viable for a few months.

Trichodina is one of the easiest protozoan parasites to detect under the microscope as it is almost perfectly round with hundreds of hooks which resemble cilla around its periphery and it constantly rotates as it moves through the mucus, causing tissue damage.

It attacks both skin and gill tissues of our Koi, and can often cause more damage to gills than realized. Classed as a warm water parasite, it can survive for some time without a host. It causes vegetation of the skin giving rise to a grey white opaque appearance on the body of infected Koi which exhibit the classic symptoms of flashing, rubbing, and lethargy.

ProForm-C is the preeminent broad spectrum malachite green & formalin treatment. The safest and most effective treatment for Trichodina and many other fish diseases.

Scales and Skin

The cellular layers of the skin consists of an epidermis, dermis, and hypodermis. The epidermis (outermost cellular layer) is very thin, usually only 6 to 8 cells thick and contains unicellular mucous glands with a network of very small capillaries. The dermis (middle layer) contains the scales, the scale forming cells, pigment, blood vessels, and nerves. The hypodermis is a vascularized fatty layer between the epidermis and the muscle or bone beneath. It is the interface between the skin and the rest of the body.

All Koi scales are of the cycloid type and most koi have scales over most of their bodies but lack scales on the head. These scaled Koi are referred to as wagoi in Japanese.

Some Koi have scales only along the dorsal line and the lateral line; these are called German scaled Koi (Doitsu, in Japanese). Some Koi are scale-less and are referred to as leather Koi. Other Koi have heavy scales appearing almost randomly and are referred to as armored scaled Koi.

Scales are thin flexible plates with a layered structure that grow from the dermis. Note that since the scales are produced in the dermal layer, removing a scale creates an ulcer, or hole in the skin, which can be a potential area for pathogens to enter the body. The scales grow essentially from the center outward. The actual origin of growth is in the center of the scale.

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Tumors Koi may suffer from internal or external tumors. Many are cancerous; others are not, so this is a case of seeking veterinary advice.

Internal tumors will only become apparent when a swelling is noticeable but may show themselves by the Koi losing its appetite or acting in a manner different from its former self.


  • Tank with matched temperature water for holding fish
  • Battery operated aerator (like Big Bubbles from K-Mart, with air stone, need
  • D Cell batteries
  • ChlorAm-X
  • Hydrogen Peroxide (for emergency aeration at .2 cc per gallon)
  • Salt
  • Malachite green and Formalin

Aqua Medi Koi Food

Aqua Medi Koi Medicated Koi

Medi-Koi™ is a custom made, slow sinking pellet that brings the medication to the bottom of your pond where your sick fish tend to stay.

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Koi Salt Bath

The simplest, and yet one of the most effective, cleaning treatments for Koi is the addition of Pond salt to a quarantine tank. The alternative to home treatment is to see if a Koi dealer would take your ill Koi for hospitalization and treatment.

When you appreciate that water is to Koi fish like air is to humans, you begin to appreciate why water quality is so important to Koi.

Poor water quality will kill your fish faster than anything else. Low oxygen in a pond can kill every fish in the pond overnight. High ammonia levels can kill fish within several days. But, even marginal levels of oxygen, ammonia and nitrates can set your fish up to fall victim to other life threatening problems. So, the goal should always be to have the best water quality possible. There are basically five water quality items you need to be concerned with, ph, ammonia, nitrite, nitrate and oxygen.

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KOIZYME 32oz $48.00

KoiZyme will reduce the bacterial count of Aeromonas, Pseudomonas and other pathnogenetic bacteria. KoiZyme is a biological formula of naturally occurring bacteria, enzymes and micro nutrients.

The Fish Immune System

A fish immune system has two parts-the cellular part that include white blood cells and other hunter-killer cells that actively seek out and ingest pathogens or diseased cells, and a chemical part that consists of antibodies, along with other important compounds such as interferon and complement.

The various parts of the immune system function best at the fishes preferred body temperature. A carps white blood cells have their highest activity and proliferation at around 83° F, falling off at temperatures above and below this point.

Antibody production is optimal at 66° to 70° F.

Metabolic Processes

Koi's metabolic processes is tempreature related. The normal functioning of enzymes in the body depends upon the fish being within an optimal temperature range. Below this range, the enzymes will stop working, and above it they become damaged or denatured. Which is why you stop feeding your Koi at 50° F.

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Most common reason Koi fish die.

  • Poor water quality 33 percent
  • Parasites 25 percent
  • Ulcer disease 15 percent
  • Predators 10 percent
  • Lack of Oxygen 6 percent
  • Medication overdose 4 percent
  • Jumping out of water 3 percent
  • Virus 2 percent
  • Toxic pesticides 1 percent
  • Tumor 1 percent

Koi Herpes Virus

A highly contagious viruses that can quickly kill your Koi is KHV or Koi Herpes Virus.

Koi which have KHV may show symptoms similar to many other diseases, such as severe gill damage and disintegration of the gill filaments, the production of vast amounts of excess mucus, loss of color, and severe internal problems due to the way in which this pathogen liquefies the internal organs.

KHV is a virus and although steps are being taken to develop a vaccine to protect Koi from it, at present there is no cure. Click Here to read more about the

Koi Herpes Virus.

Koi Health Ailments Beginning

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