Prevent Koi Disease | Remove Stress To Maintain Healthy Koi

Stress Removal Is Essential to Maintain Disease Free Healthy Koi

This article is part 4 of a step by step guide on how to successfully keep koi in your own back garden.

The previous articles have looked at the Koi's environment and how by getting this right you significantly increase the chances of successfully keeping koi.

This article takes a look at your koi and how by simply removing stress from their environment, you can help to prevent koi disease and maintain healthy koi ... Click for other Successful koi keeping articles ...

Preventing koi disease Versus Maintaining healthy koi

Koi, a form of carp, is like any other fish in that the vast majority of it's being is water (approx four fifths or 80%). This by definition means that koi will be affected to a large extent by the quality of the pond environment it lives in.

We need to be able to differentiate between how to prevent koi disease and how to maintain healthy koi, for the simple reason that it is easier to manage both as separate concerns. Of course each does have an effect on the other but to be able to manage both correctly it is easier to treat them as separate issues.

On many occasions we can link koi disease or ill health to poor water quality conditions e.g. low oxygen or higher than ideal levels of ammonia or nitrite. It is important to ensure that the following are adhered to:

Low nitrate levels (max 50ppm)
Zero ammonia and nitrite levels
Sensible fish loads (stocking density)
Effective biological filtration
Quality diet
Effective pond water circulation
Stable water conditions
Mineralization and regular partial water changes.

Maintaining healthy koi, who are happy in their environment will help reduce the opportunity for disease to take effect.

Stress and the impact it has on koi health

The major cause of disease in koi is stress. It is not strictly the stress itself that causes illness but the effect stress has on the Koi's super efficient immune system. Stress is an all encompassing term covering aspects including, changes to water conditions or the koi's environment. When your koi experiences stress this doesn't necessarily mean that it will fall victim to disease causing organisms but it does increase the opportunity for disease to occur.

When a koi is stressed the first that happens is a release of adrenalin, particularly in a situation where it needs to make a quick getaway. The adrenalin allows the koi to take flight but has serious implications to it's salt/water balance (osmoregulatory function). This can seriously affect the Koi's immune system, allowing disease to take a foot hold.

Koi produce mucus which acts as a barrier against it's environment and a defensive barrier against parasites. When the water conditions deteriorate substantially, excess mucus is produced. This excess encourages the growth of parasites, particularly Costia and Trichodina, that feed on the mucus.

A Koi's immune system, particularly the ability of it's white blood cells to fight disease is hampered by the release of Cortisol, a hormone released in response to stress. This harmful side effect yet again increases the susceptibility of koi to illness and disease.

Ideally we should remove the stressor as soon as we become aware of it's presence, so as to maintain the health of the koi. We should for example replace the water (ammonia / nitrite reduction) or improve the levels of oxygen. If the stressor is a bird or cat, we should endeavor to prevent them from making frequent visits.

Having removed the stressor it is important to realize that it will take some time, perhaps weeks in some cases for your koi to return back to peak, stress free health. In the mean the koi will still be susceptible to pathogens and subsequent illness.

Where does koi disease come from?

It is impossible to prevent water borne bacteria and other pathogens from entering into the pond environment. Although a UV sterilizer (UV clarifier) will help to eradicate some this is by no means a guarantee. In nature koi and pathogens live in harmony and just as koi are opportunistic feeders, so are pathogens. A stressed koi presents a perfect opportunity and one that will be taken. Having accepted the fact that we can't eliminate them altogether we need to decide how we can control these disease causing pathogens.

It is possible for bacteria, viruses, fungi and parasites to enter the pond environment via airborne routes, however the majority of introductions are as a result of negligence on the pond keeper's part e.g. introducing new fish fish into the pond environment, without allowing for a period of quarantine (acclimatization). It is important to quarantine new koi, not only to prevent the introduction of disease causing pathogens (bacteria, viruses, fungi and parasites) but also to allow you to become familiar with the behavior and personality of the new koi. Quarantine also allows the new fish to have a well earned rest, after it's long journey from Japan. Studying the behavior of new fish is important so as to allow familiarity. Familiarity will in future allow you to spot changes in behavior, often an indication that the fish may be ill or stressed (discussed in more detail in article 3 - Koi Husbandry And Understanding Koi Behavior Patterns.

As the new koi becomes acclimatized the levels of pathogens being carried will drop, therefore reducing the risk of disease to the koi living in your main pond. Having said this a virus known as KHV, will remain ever present in your new koi, irrespective of the length of time the fish is quarantined. However by providing a stress free quarantine environment it's chances of attacking are considerably weakened.

Ways of preventing koi disease

Familiarity by regular watching will help you to spot when something isn't quite right
A quarantine period or period of acclimatization
Routine dosing in the fall and spring against parasites, fungi and bacteria

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