Preventing and treating some common diseases when raising Koi fish

Currently there are many types of diseases that occur with Koi fish. There are long-lasting contagious diseases that cause epidemics that kill fish. In particular, the main reason is due to our improper care. Therefore, you need to know how to take care and protect fish.

White spot disease:

White spot disease or white fungus in Koi fish is one of the most common manifestations, when the white fungus will eat the cells and fluid under the skin and will gradually kill the fish, so it should be treated promptly.


Causes : White fungus disease occurs when the air humidity is high, the environment temperature is low or the dirty aquarium causes white fungus to grow and penetrate Koi fish.

Disease manifestations:  On the skin of the Koi will appear white spots up causing Koi fish to swim lethargic and anorexia.

yoke:  When you see fish appear signs of white spot disease should catch fish in a separate tank or pot and then drop methylene blue (3-5 drops) or use specialized fungicides sold at the fish shop. Besides, it is necessary to effervate the aquarium water and use it to raise the temperature (at 30-32 degrees Celsius). When the fish are cured, they will be returned to the large tank.

How to prevent white spot disease: Make  sure the water in the lake is always clean by improving the water filtration system to keep the water clean. The water supply for the aquarium must also be clean, newly bought fish should be disinfected before being added to the tank.

Warts (Pinecone Disease)

Signs of disease:  Swollen body, ruffled scales, protruding eyes, fish eat less, swim slowly.

How to handle:  Take the disease in a separate pot and then fish with salt water (concentration of 3-5kg / m3) bath for 5-10 minutes in combination with aeration several times. Bath fish continuously for 5 - 7 days until the condition improves.

Treating tail rot:

Signs of illness:  The tail or fins of an infected fish will show tattered, rotting, lazy swimming fish, eat less. The disease should be treated quickly to avoid the risk of death.

Treatment:  Remove diseased fish from the tank and keep the tank, separate tank. Use medicine to treat fishtail rot (can be purchased at ornamental fish shops or veterinary medicine stores, use the medicine as directed).

Take out other fish and proceed to clean the tank, so wash the tank with hot water, wipe the nook of the tank, do not use tap water to wash. Soak accessories in hot water for 5 - 10 minutes then rinse. Then proceed to replace all the water for the aquarium (dechlorinated water or use filtered water).

Check pH in tank before putting fish in. If the pH is not sure, you can put antibiotics or antifungal into the water to kill bacteria. Add oxygen to your fish by creating a stream of water to flow into the lake or adding aeration machine. Should eat the amount of a moderate, right meal.

Mouth rot.

Koi mouth disease or foot-and-mouth disease looks like a fungal disease, the cause of which is caused by the columnaris bacteria - a gram-negative rod-shaped bacterium, this bacteria usually resides in the mouth of the fish. in the fish's mouth. Often when fish has a weak immune system, it is more susceptible to this disease.

Symptoms:  The area around the mouth of the warty fish looks like a lump of cotton, usually yellowish brown, white, grayish white with red spots on the head or fins and gills.


Use Melachite green (not for fry), Melafix or antibiotics (Spectrogram, Furanace or Sulfa) to apply to fish.

Do not increase the water temperature will cause bacteria to flare up, making the disease worse. Note to prevent disease, it is necessary to avoid sudden increase in lake water, ensure clean water, do not feed excess fish, do not raise fish too much, need to regularly clean the tank.


There are several types of parasites that cause Koi fish, depending on the type of parasite that divides the diseases: fish lice, wheel infections, fluke, parasitic diseases ...

Disease manifestations:  The common manifestation of parasitic disease is that the skin of the fish becomes more viscous, the mucus is broken, the skin is destroyed, ulcers are present.

How to handle:  Take the fish into a separate pot and then put in potassium permanganate, about 100g / m3 concentration, for the fish to bath for about 1 hour. Bathe once a day, shower continuously for about 2 weeks and monitor the disease. In addition to using purple drugs, you can also use Formalin, alum green (CuSO4), Potassium dichromate (K2Cr2O3), Hadaclean. Use as recommended by the manufacturer.

Need to change the entire tank water, cleaning the aquarium.