Koi are no different to humans, when it comes to illnesses and diseases, they are also susceptible to all the nasties out there, just like us. Koi are extremely tough and hardy creatures, but they too develop illnesses if the following criteria are not upheld:

AERATION: Fish breathe oxygen in the water through their gills. If the water does not have sufficient aeration the fish will suffocate or it will increase their stress levels.

WATER CONDITION: Checking your ph and ammonia, nitrite levels, making sure that you have a good filtration system.

WATER CHANGES: Do small, regular water changes on a weekly basis.

CROWDING: Do not overcrowd your pond as this places a great deal of stress on your fish as well as on your biological filter. Overcrowding is one of the major reasons for health problems.

FEEDING: Do not overfeed and make sure that your fish are getting the right nutrition.

INJURIES: This is quite common, treat it immediately if you notice injuries.

CIRCULATION: Make sure that there is good movement in the pond, stagnant water is not good as bad bacteria grows well in stagnant water.

It is advisable to follow the above guidelines to prevent health problems. The good old saying "prevention is better than cure" applies here.

If you take the right approach in maintaining your pond, your fish should be fine, although minor ailments do occur even under the best conditions.

If you have problems with your fish, the problem will probably be either a virus, Bacterial infection, Fungi or Parasites.

 KHV, being Koi Herpes Virus, is the worst possible problem because there is no cure. (see symptoms below)

Other possible viruses in a Koi pond are SVC(Spring Veremia of the Carp), or carp pox, which can also not be treated

2  Bacterial infections

Often followed by a parasite infection and caused by bad bacteria (normally Aeromonas and Pseudomonas)

Causing fin rot, gill rot, ulcers, dropsy and mouth fungus and it is contagious. If one fish in the pond has a bacterial infection, you normally have to treat the whole pond.

Diagnosis: normally cotton wool like growths on the body. Fortunately fungus is not contagious.

The most common problem and often causes bacterial infection.

It attacks the interior and/or the exterior of the fish.

Some are visible like the Anchor worm, White spot and Lice, but most of them are only visible under a microscope like Fluke, Costia and Trichodina.

Treatment is quite affective and 90% of parasites can be killed with salt.

FIN ROT: This is a bacterial infection resulting in split fins caused by stress, bad bacteria, poor water conditions, or low oxygen levels.

FLASHING: If you notice your fish scraping themselves on the bottom or sides of the pond, this is a good indication that the fish is carrying parasites.

HEAD HANGING: This could be caused by flukes, one of the most annoying parasites, and should be treated immediately.

MOUTH ROT: Whitish growths around the mouth.

WHITE SPOT: The body and fins will be covered in small white spots.

SLIME: This is a greyish film on the body.

ULCERS: This comes across as open sores on the body.

GILL PARASITES: Mucus forms on the gills, and the gills become inflamed.

These are just a few of the common problems you may encounter during your years with your fish, but with the treatments that are available(all included in the medicine chest), these problems can be rectified easily.

One of the most serious diseases are KHV - This means KOI HERPES VIRUS. This disease is at this point incurable and can wipe out your entire pond in a matter of 2 weeks and affected various ponds from breeders and hobbyists recently. This virus only attacks the common carp and koi.

Only buy fish from reputable dealers, breeders and koi keepers who know about the existence of KHV, and who quarantine their fish against this and all other infections and bacteria. Please quarantine all new arrivals that you purchase.

Short summary of signs to identify possible diseases.]=

- fins closed - Ick

- breathing difficulties - Flukes

- Stress/off colour - Cloudy eye

- flashing - Flukes, ph

- gasping at the air - not enough oxygen

- rapid gill movement - Ick

- sitting on the bottom - Flukes or swim bladder disease

- restlessness - Lice, Fluke

- wild swimming - check ammonia levels

- jumping - parasites

Bacterial infections are the most common reason for serious health problems and deaths.

There will always be bad bacteria in a pond. The secret is to keep it as low as possible because the Koi can only defend themselves against these bad bacteria up to a certain point.

The infections normally occur during spring as they are not active below 15 degrees Celsius and the immune system of the Koi is still very low this time of the year.

They are caused by overcrowding and poor water quality and normally follow a parasite infection, when the immune system of the Koi is even lower.

Prompt action is the key to success because it is very difficult to treat once the bacteria enters the fish, in which case you have to treat from within. If you suspect a bacterial infection, immediately do the following:

Do a 30% water change

Take all plants out and add 4kg of salt per 1000 liters. This will create a mucus coat to prevent the bacteria from attacking the fish, it acts as a disinfectant, it kills 95% of parasites and bacteria and it combats the effect of excessive water entering the Koi through it's wounds/ulcers(if any) and it lower the effect of possible Nitrite poisoning. We believe that the average Koi keeper should stay away from chemicals as long as possible and stick to the more natural safest ways of treatment. That is why were recommend salt as a first treatment. Add 5g of Virkon S per 1000 liters and keep the high salt level for two weeks and do regular water changes (20% every 4 days or 10% every second day) Maintain perfect water quality and decrease food intake until the bio filter is fully active again, unless the bio filter was bypassed.

Maintain a fairly high level of salt hereafter, about 2.6 kg per 1000 liters.

If Ulcers and/or fin rot already appeared, make a paste with hydrogen peroxide and Methylene Blue or Malachite green and apply directly onto the wound. The wound should then be sealed with Friars balsam.

Treat with Malachite green (1g / 1000 liters) to assist the salt with disinfection. Increase aeration and put UV light off.

If not successful, treat with potassium permanganate. (2.56 g / 1000 liters) until the water stays pink for at least 8 hours. It might be necessary to do up to 4 treatments a few days apart to achieve this result.

Increase aeration and put the UV light off and remember, your dosage with potassium is extremely important. Be sure to calculate the volume of your pond accurately.

If it is a very valuable fish involved, consult with a vet to proceed with anti biotic injections, but only if all else fails.

FISH LICE OR ARGULUS

Fish lice is an external parasite which can be viewed with the naked eye unless it is still very small.

Treatment: Once off treatment with Trichlorfon at 1 g / 1000 liters or Dimilin at 1g / 1000 liters

COSTIA

One of the most common parasites found on koi in South Africa is Costia, which has killed numerous of our precious Living Jewels.

Also known as Ichthyobodo, it is an external parasite that is quite difficult to identify, even with a microscope. You need at least a 200 x magnification to properly identify it, and one of those cheap R 300.00 microscopes is not recommended to identify Costia. It is one of the smallest parasites common to the Koi hobbyists and is often overlooked on a slide.

When viewed under the microscope, it looks very similar to the tiny moving air bubbles in the water, except that the air bubbles will move into one direction, and Costia will move backwards and forwards, almost like bumping cars at a play park, trying to dig through the mucus on the slide.

Physical symptoms on the fish will be excess mucus production, lethargy, clamping of fins and scraping.

You will probably notice reddening of the skin and especially the fins. If you see that your koi hangs at the air stones or water returns, it is normally an indication of the presence of Costia.

Fortunately it can be eradicated quickly with a high concentration of salt(5kg/1000 liters), but if you don't treat early enough, you might loose fish, especially the small ones, as Costia develops rapidly on small fish. A salt bath at 1 kg / 50 liters will also do the trick.

Other recommended treatments are FMC, Malachite Green, Potassium, or even Methylene blue, and a once-off treatment is normally sufficient, due to the very short life span of Costia.

　

A quite common parasite is the Anchor worm.


Also known as Lernaea, it is an external parasite which you can view with the naked eye. It is a true parasite in that it lives on the fluids and tissue of the fish itself.
They range from 5 - 13 mm in length and are normally off white or black.

They anchor themselves on any part of the koi and in the process puncture or creates a hole in the body. See the image above. This again, creates the possibility of bacterial infection and consequent death.

The koi will move erratically trying to get rid of the worm or flash, and that also creates open wounds because they often damage themselves in the process and consequent secondary bacterial infection often follows, with possible death.

They are quite common on koi which have been harvested recently from mud dams.

Treatment:

First of all, you have to get rid of the worm by gently removing it with tweezers. Then, it is vitally important to sterilize the wound with Hydrogen Peroxide and thereafter with a very strong concentration of Potassium, Malachite Green, Methylene blue or another suitable topical antiseptic.

Secondly, you have to inspect if bacterial infection were created. If so, you have to treat for bacterial infection first. In a case like this, I personally treat with Potassium, because it will address the bacterial infection and it will sterilize the wound and it is also a bit effective against Anchor worm.

Thirdly you have to get rid of the worm in all its stages. Use Dimilin or Trichlorfon @ 10 g / 10 000 liters and follow up the treatment after five days to get rid of possible newly hatched worms. It is also a good idea to increase your salt levels to 3 kg/1000 liters to prevent infection.

If you treated with Potassium for bacterial infections, do the Dimilin or Trichlorfon treatment only after the water turned brown from the Potassium and only after a 30 % water change.

If you did not treat with Potassium, it is a good idea to add Virkon S to your pond water to decrease the bacterial count to prevent a bacterial infection.

　
Chilodonella can be identified by the small hair (cilia) on the body, especially on the longer side of te body and can only be identified only with a microscope.

It can swim, using the cilia, and can therefore attach to your nets and filters.

They attach themselves to the koi, causing irritation.

Your koi will probably hang at the bottom, separate themselves from the other, and the fins will probably be clamped against the body. It will also probably flick or rub themselves against the bottom or sides of the pond, causing secondary damage. They will also loose their appetite.

They normally cause havoc during winter when the water is very cold, and very seldom cause problems during warm summer periods.

The best treatment is a combination of Malachite green and Formalin(FMC) if you do not have salt in your water.

If you do have salt in your water, increase the salt concentration to at least 4kg/1000 liters and/or treat with potassium permanganate at 2 grams per 1000 liters.

A mpeg video of Chilodonella can be downloaded and viewed from our web site.(360 kb)

White spot can easily be identified from white spots on the body in it’s mature state as the name indicates. When white spot has reached its mature state(when you can notice it without a microscope), it is difficult to kill them as it is embedded between the top two layers of the skin. You must try to kill the free swimming stages, and therefore you need to treat at least three times, with a few days in between. The best treatment for Whitespot is FMC at 15 ml / 1000 liters. You have to treat three times with three days in between. Alternative treatments are high concentrations of salt (5kg/1000 liters) Malachite Green. Methylene Blue or Formalin.

The most feared virus is KHV. Typical symptoms of KHV are:

- GASPING FOR AIR

- SUNKEN EYES - This is the most advanced stage of the disease.

- MUCUS - This is secreted by the skin, followed by dry patches.

- HEAD HANGING - Down for long periods of time.

- SEVERE GILL NECROSIS - that gill tissue breakdown.

- ULCERS - sores appearing on the body.

- HAEMORRHAGING

- DEATH - within 2 weeks.

PLEASE REMEMBER: Some of the symptoms can be related to parasitic/bacterial infections, caused by poor water conditions. PLEASE don't assume that this is the KHV virus, until you have an accurate diagnosis which can only be done in Durban by MDC. For more details, please visit our web site.

Up until now, no treatment has been found for KHV, but there are treatments available to prevent secondary bacterial infections. There are vaccines available from Israel, but are not being used in South Africa, because it is believed that the vaccine may spread the virus. If you increase the water temperature above 28 degree Celsius, you might kill the virus, but the fish will still be a carrier.

Hi-Kui is not contagious and in real terms it has no effect on the overall health of the Koi, as long as the system in which they are kept is of a suitable standard. The main effect of Hi-Kui is cosmetic. It degrades the appearance of your Koi.
There is no treatment to cure the surface of the skin on the Koi, as there will always be a mark of colouration be left on the spot where the Hi-Kui was.

Treatment:

Clean the area and dry really well. Scrap the infected area with a blade or back of a knife.
This will come off just like jam. It is essential that you remove the entire red grunge. After that clean the area with Hydrogen Peroxide Volume 10, and dry off really good. A hair dryer set on cold will achieve this very well.

You could use a Potassium Permanganate paste, but it could be aggressive if you are going to stand a chance of the red coming back to its former glory. Let the paste dry (use the hair dryer) and cover the infected area with friars balsam. You can also freeze the area with lighter gas, and cover it with friars balsam.