Especially in the heat, koi are susceptible to bacterial diseases. Which bacteria are. What can be done against it? These unicellular organisms can act in very different ways. There are bacteria that colonize the koi and damage them by harmful excretory products. But there are also bacteria that feed directly on the fish tie. In today's guide there is an overview of diseases which are caused by bacteria.
Classification of bacteria
Bacteria cannot be seen with the naked eye, a microscope is really necessary. But the damage can be seen on the koi. Bacteria are very differently shaped. They can be spherical, rod-shaped or elongated. They can occur solitary or be organized in groups. In Koi keeping there are two groups of bacteria that play a role in diseases:
– Obligate pathogenic – these bacteria cause disease in a healthy animal with a healthy immune system – Facultative pathogenic – these bacteria cause disease when the animal and therefore the immune system is weakened
The former do not occur naturally in the pond and if they get into the water, it is necessary to react. The second mentioned are always present in the water or also at the fresh water. If the ecosystem is in its balance, these bacteria even have positive effects on the entire system. However, if this gets out of balance, then these bacteria can also cause disease. This can happen, for example, if these bacteria get into an open wound and multiply there.
Diseases and their causative agents
Different bacteria can cause different diseases. Here is only a small overview. The pathogens Aeromonas or Pseudomonas cause fin rot. The fins are attacked and fringe out, the scales lose their shine and at the base of the fins there may be bloody spots. Mycobacteria are the pathogens of fish tuberculosis. Pre-swollen eyes or a sunken belly can be signs of an infestation. Different bacteria can cause pitting disease. Scales lose their resistance due to poor water values. The bacteria settle into small wounds and cause the holes to enlarge down to the skin. A bacterial infection can lead to Saprolegnia, a mold infection, which can be recognized by white, frayed spots.
Treatment of sick fish
If koi have a bacterial infection, then antibiotics should be used as therapy. These are substances that either destroy the metabolism of the bacteria or even their structure and thus kill them. However, these antibiotics must then be used exactly according to instructions. Bacteria multiply very quickly and with incorrect antibiotic administration, the bacteria can develop resistance and the antibiotic is no longer effective. Unfortunately, these resistances are increasingly becoming a problem in fish farming, as antibiotics are used en masse or even incorrectly. If a germ has developed into a multi-resistant germ, the affected koi is then often beyond help. Therefore, such treatment should always take place only in consultation with a veterinarian.
The treatment can be done in different ways. The koi can be separated from the other fish in a special holding tank in the pond and the antibiotic can be added to the water. This is a so-called bath treatment. Here, however, large amounts of antibiotics are needed. The effect can already be affected by small impurities in the water.
The antibiotic can be administered through the feed. Then the lining is soaked in the medicinal substance. The prerequisite is that the fish still eat. However, it is then difficult to keep to the single dose per animal. Also, the water dissolves the antibiotic out of the lining again. So a rather difficult method. It is most accurate when the fish being treated receives the antibiotic as an injection. Injected into the muscles, it spreads from there with the blood throughout the body. However, the Koi keeper should be skilled in this method.
Prevention of bacterial infections
A koi loses its resistance when the pond ecosystem is out of balance. This is usually due to poor water values, which put the Koi in a stressful situation, making it more susceptible. Therefore, it is important to regularly check the water levels (Advisor: Water values in the pond). If it can be seen that an animal is ill, it is advisable to remove it from the pond so that the other koi are not infected. Until the animal is fully recovered, it can be kept in quarantine.