A koi falls ill as we humans do. Therefore, when it is diagnosed to be ill, it is, in many cases, too late for treatment. The best way to avoid and minimize the contraction of diseases is early detection and early treatment.

1. Please notice following points for early detection. If you take a good look at the koi every day, you will not miss the slightest change in their attitude.
Please be careful of changes in their external surface (partial congestion loss of gloss and white membrane). A diseased fish begins to swim away from the group it has belonged to. When the diseased fish comes to swim unsteadily like a sleepwalker or bump into the wall of a pond or aquarium, it is a sign of its being in a serious condition. Also when the diseased fish comes to rub itself against the wall of a pond, it indicates that it is in a critical condition.
Please watch out for a fish lying on the bottom of a pond or leaning against the wall with its pectoral fins extending out, and a fish gasping with its mouth widely opened.
If you find one of the fish in a group showing bad appetite, vomiting or discharging clear, watery faeces, you need to know that the fish is in trouble.

2. Treatment

There are different kinds of treatment including oral administration, medicinal bathing therapy, a local remedy and injections according to each one of symptoms but I recommend you to consult with a man in your nearly koi shop. I think it safe. The key is that you should lose no time in discovering any disease and doing something.

3. Diseases

1) Raised Scales

Symptoms :	Scales over the body get up. The fish are most likely to catch this disease early in spring, but in a high water temperature they have less possibilities.
Treatment :	A 10 days' medicinal bath in a solution of 100 ml Parazan D/ton and 5 kgs salt/ton.

2) White Spot Disease

Symptoms :	Small white spots appear all over the body and the fish looks as if it were dusted with powder all over the body. This disease are most likely to break out within a water temperature range between 10 to 15-degree C, and it is cured when the water temperature goes up above 29-degree C.
Treatment :	A 7 days' medicinal bath in a saline solution of 5 kgs/ton.

3) Fungus

Symptoms :	The surface of the body becomes cloudy because of bacteria, and the fish looks as if it were covered with white membrane. The diseased fish loses its appetite, goes to the inlet of water or the corners, and rubs its body against the wall. This disease are most likely to break out at the water temperature of 15-degree C.
Treatment :	Both a formalin and a potassium permanganate medicinal bath are effective. A salt bath (5 kgs/ton) is the easiest.

4) Mouth Rot Disease

Symptoms :	Congestion appears around the mouth and promotes its color to red or yellow. Then the disease part starts to go rotten.
Treatment :	An oral administration using antibiotics or a long-term Parazan medicinal bath (200 ml/ton).

5) Fin Rot Disease

Symptoms :	The tail fin gets red and congested, changes its color to white and goes rotten from their ends.
Treatment :	The same as the case of Mouth Rot Disease.

6) Gill Rot Disease

Symptoms :	This is the disease which fish catch most. It often happens that a fish is found dead with its gills congested. Please discover changes in attitude from signs a fish is showing as soon as possible : loss of appetite, slow movement and separate action. When you guess something is unusual, check out the gills. The grayish-white gills tells you that this is it.
Treatment :	An oral administration using antibiotics or a long-term Parazan medicinal bath (200 ml/ton). Or a medicinal bath of Terramycin (50 g/ton) and salt (5 kgs/ ton) for ten days.

7) Anchor Worm

Symptoms :	A 1 to 2 milimeter-long, threadlike anchor worm sticks to the body under the scales. A fish infested with the anchor worm jumps and rubs its body against the wall of a pond. It is macroscopic.
Treatment :	A Mazoten medicinal bath (0.2 -0.5 g/ton) is effective for anchor worms in their larval stage, but not for the adults. The adults need to be pulled off with tweezers.

8) Fish Lice

Symptoms :	The fins are infested with fish lice each with a length of 5 milimeters and a width of 3 milimeters. The diseased fish jumps and rubs its body against the wall in the same way as the fish infested with anchor worms. It is macroscopic.
Treatment :	An adult louse can be eliminated in a Mazoten solution (0.2 -0.5 g/ton). The use of tweezers is effective as well, and it needs to be repeated a few times.

9) Hole Disease

Symptoms :	The appearance rate of this disease is high. First of all, white spots as large as a grain of rice turn up, its diseased parts gradually spread all over the body. When the diseased parts get congested and some of the fins are about to come off, it sometimes happens that the bones are exposed. The mortality is low, but the fish, if cured, may have keloids on its body.
Treatment :	A Malachite green medicinal bath (0.1 -0.2 g/ton) for seven days or an oral administration of antibiotics is effective. An injection of Canamycin works.

The outbreaks of these diseases mainly result from water turbidity. Please keep it in mind that nothing is better than early detection and treatment if you want to protect your koi from diseases. If you have something worried about your koi, you don't have to hesitate to ask someone in a koi shop for advice. A koi is a precious living thing. Let's try to keep a careful observation every day.