It is important to remember that only a few of the diseases contracted by koi are visible with the naked eye. The serious hobbyist usually has a microscope handy to enable him/her to identify the diseases accurately. Subscribing to the South African Koi Society also benefits the hobbyist with useful information on a monthly basis. Should you need urgent assistance please feel free to contact us. We can also assist you to locate a knowledgeable person/organization within your area.

There are a myriad of diseases a koi can contract. Almost all the diseases carried by koi are directly related to either water quality or stress.

DISEASES THAT CAN BE SEEN BY THE NAKED EYE:

Carp Pox:

Carp pox is waxy white lumps that form on the body and fins of koi. They are more prominent during the change of seasons and especially in the beginning of spring. The causes of carp pox are controversial but it is mostly believed that carp pox is genetically transferred. It is therefore not advisable to breed with a koi that gets carp pox.

You will notice that the carp pox disappears as soon as the water temperature rises.

Carp pox is not a life threatening disease.

There is no known cure or treatment for the disease. The best you can do is wait for the water temperature to rise and make sure the water is kept as healthy as possible.

Ulcer Disease/Dropsy:

Also known as dropsy or abdominal distention, is usually caused by Aeromonas or Psaudomonas bacteria. Affected fish show ulceration of the body, a swollen abdomen, protruding scales, and swollen eyes. The bases of the fins can become inflamed. Fish tend to be listless, stop eating, and lose their normal coloration.

Disease outbreaks are correlated with environmental factors. In koi, outbreaks usually occur in the spring, but the disease can also occur during the summer, especially if the fish are stressed by chronically low oxygen concentrations.

Infected fish should be treated by adding appropriate antibiotics to the food. The addition of antibiotics to the pond water is not recommended since the disease is an internal process, and most medications are unable to be absorbed from water in sufficient quantity to be effective. Aqua101 or Baytril Powder should be added to the paste food. Antibiotic injections are fast working but should be administered only by an experienced person. It is quite easy to kill a fish with this process, either via the wrong dosage or incorrect handling of the koi whilst anaesthetized.
To stop further infection dress the wound with a wound sealer.

Flashing:

Although the cause of flashing can not be seen with the naked eye, the symptoms are clear and therefore can be treated well in advance before disaster strikes.

Flashing is when a koi scratches it's side on other surfaces on the bottom or sides of the pond - or on an ornament. Flashing only becomes a problem when the koi do this excessively. Remember just as your back itches from time to time theirs do too.

Koi will flash and scratch when they have Flukes, Trichodina, almost any parasitism can cause fish to flash or scratch on things. One problem is that the parasites damage the skin, opening it to infection. The other problem is that the fish damage their own skin when they flash, so you need to get them to stop.

Another important consideration is that changes in water quality can cause flashing. A large freshwater change can cause flashing as the fishes' skin adapts to a slightly higher or lower pH. A dramatic reduction in dissolved organics causes a tingling in the skin.

No matter what you ultimately do about this condition, please, first, check your water for Ammonia, Nitrite, and Nitrate. Establish that the Ph is higher than 7.0 using any of the many great and simple to use test kits available.

To rid your Koi of the parasites causing the scraping use a strong bath of Potassium Permanganate (10 grams per 100 litres of POND water) for 4 minutes. Oxygenate the water well whilst the koi are in the bath. If the koi shows any signs of distress remove immediately. You will most probably notice a brownish foam forming on the top of the surface – those are the parasites coming off the koi!

STRESS

Signs seen by the naked eye:

The reddening of white areas especially the pectoral and tail fin areas. The white areas on a koi will show “veins” just underneath the skin of the koi.

Excessive handling, overcrowding in ponds and poor water quality mainly causes stress amongst others.

In stressed koi the immune system is less effective, digestion is interrupted and important hormonal changes take place. In short, it is easy to see why stressed koi are more vulnerable to disease than are those kept in ideal conditions. Which brings us neatly to the constant realization that good health stems from preventing problems rather than simply curing them.

Treatment:

Add 3% non-iodized course salt to your pond or 3kg per 1000 liters of water. Stop feeding the stressed koi for at least 48 hours – they will not starve to death.
Find the cause of the stress and eliminate the problem immediately.

Eliminating stress factors:

This is just as important as providing medication to treat koi. An otherwise healthy koi may be carrying a potential disease that may well take hold when the fish is stressed or its immune system reduced. Netting and handling healthy fish properly is just as important as the treatment process. Carry out handling tasks with great care at all times. Quiet surroundings will help keep stress to a minimum.

Using a sock net:

If unfamiliar with handling koi out of water; a handling sock may be a useful addition to your box. This is a tube of fine nylon mesh about 1 meter long and open at both ends. One end has a handle attached and the fish is encouraged to swim into the sock at this end, the other end being gripped to prevent it swimming straight through. With the fish in the center of the sock it can be safely lifted, carried and released into the pond by relaxing the hold on the “open” end of the sock. The fish will then swim out. A reasonable sized koi can be slippery, and difficult to control when “flicking” its powerful tail. Using a handling sock will take away the risk of dropping such a koi.