All about Koi diseases and treatments: how to tell if your fish are sick, what illness they have and how to cure them
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Throughout history, fish have been true survivors. Carp have been dated back to around 20 million years ago, making them one of the oldest species of fish around. In that time, they have developed great immune systems, protecting them from harsh changes in the climate, a lack of food, and even most common bacteria and parasitic illnesses. However, the Japanese version of the carp, the koi, is a different animal entirely when it comes to immune systems. Due to the selective breeding of colored “mutants,” koi have compromised immune systems and are very susceptible to illness. This is the price the fish have paid for being bred for beauty.
There are two main categories of disease in koi: bacterial infection and parasitic infection. Both can be deadly to not only the infected fish, but also the entire colony. Any illness must be spotted and cared for immediately, lest you risk losing the entire pond.
Almost anything can bring on illness with a koi pond. Although there’s no real gauge to measure the likelihood of illness occurring should you lapse in your pond upkeep, enough koi have succumb to illness to form a pretty good baseline and to advise owners that they should always be on the lookout for illness. Each time you go out to visit your koi, you should check them for signs of illness; moreover, make time to do so at least once a week.
Parasites include flukes on the skin and gills, costia, leeches, anchor worms, lice, and other parasites. You will be able to notice some parasites by your koi’s behavior and appearance. If you spot a fish constantly rubbing against rocks or with unusual white spots on their body and/or fins, this is the sign of a parasite. To treat the water for parasites, you can buy a solution over the country and also salt the water with a mild solution. Do this in your quarantine tank, moving the infected fish into the tank until cured.
Some of the bacteria infections your koi can pick up include fin rot, cloudy eye, split fins, ulcers, and other body damage. This damage is easily seen on the fish. Just like with the parasites, you want to remove the infected fish from the pond and put it into a quarantine tank. With the fish in quarantine, you can control the environment better and also isolate the bacteria from causing any sort of disease in your other fish.
However, with all diseases aside, the most dangerous factor to your fish here is the actual pond medication you use. This is why it’s important to quarantine the individual fish before attempting to mediate the entire pond. Before purchasing any type of pond solution to rid it of parasites and bacteria (bacteria being far less common with properly filtered waters), you should find out exactly what it does and in what amount you should use it in. Only medicate the entire pond if all your fish are sick. If it’s only one or two, it’s much easier to quarantine them and care for them in a controlled environment.
