Every pond owner with fish, at some time or another, will probably have to medicate their pond. Though Koi are extremely hardy, it is very important to keep a watch on their environment to keep them at their healthiest.
Attention should be paid to the quality of water and balance of the pond (i.e. pH levels etc.). However, if problems do occur, the first step is to remove the individual fish or decide whether to treat the entire pond.
It is sometimes difficult to be aware of a problem with a fish until its too late.
Be aware of your Koi's behavior patterns so changes can be detected early. A change in your Koi's behavior is usually the first sign that that your Koi are stressed or ill.
Bacterial Koi Diseases & Treatments
Fin & Tail rot. (Flexibacter Columnaris), Holes. (Aeromonas), Vibrio.
One of the prime causes of fish mortality is bacterial disease. With the exception of "columaris" nearly all bacterial infections occur after another problem has occurred, stress is a prime factor with bacterial disease. Most are gram-negative organisms.
Treatment can be varied but some treatments are Acriflavin, chloramphenicol, sulphonamides, salt, etc. as a dip, topical, or in feed.
Fungal Koi Diseases & Treatments
A secondary infection in the area of some other fish injury. Also affects damaged or disturbed fish eggs.
Treatments include: Acriflavin, iodine, Malachite Green, salt, formalin as a bath, topical, or in pond.
Parasitic Koi Diseases & Treatments
Anchor worm, Fish lice (Argulus), Flukes, Ich, Internal parasites.
Most fish carry parasites, but older fish develop a degree of resistance that prevents problems. Parasites like anchor worms and fish lice usually are a problem whenever present. Young fish are more susceptible to illness caused by parasites. Stress situations and seasonal climatic variations can bring on infections.
Treatments include: Dylox, Masoten, Demilin, Formalin, Malachite Green, potassium permanganate or salt in the whole pond or in a bath.