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Non Contagious Diseases

Fungal Infections (Saprolegnia)


Fungal infections as we know it in koi and koi ponds are caused by different groups of organisms. These organisms include true Fungi and water moulds.  Perhaps the most common “fungal” infection is Saprolegnia, which is actually classified as a water mould (Oomycetes) and not a true fungus.  Moulds reproduce by releasing thousands of spores into the surrounding water and are therefore ever present, regardless of how sophisticated the filter systems are. The fungal spores are highly resistant to drying and chemical attack and thus Saprolegnia spores and moulds are common in all ponds and tanks. This mould in short time will cover a dead insect or uneaten food that is left in the filter. Oomycetes therefore forms part of the process in the filter system that breaks down trapped waste.

Last Updated on Monday, 06 December 2010 15:28


Dystocia (Egg impactation)

Dystocia is a term that comes from the Greek word, meaning bad birth or difficult birth. Anyone who keeps koi will at some time come across a case of dystocia or egg binding, or sometimes called egg impaction, in a mature female. The condition will be evident in mid-summer, although in some instances things can go wrong in early spring.


Last Updated on Sunday, 31 October 2010 22:26


Tumors in Koi


Tumors happen in fish, just like in other animals and humans. The cause of many of the tumours and malformations found among Koi are for the most part poorly known, because studies involving fish are few and far between. The financial incentives for studies on fish are just not there. Certain malformations are caused by injuries.  Tumors occur on nearly all organs or tissues. Some tumors are caused by various ingredients in the diet. There is also a suspicion that viruses may cause certain tumors, similar to the megaloblastic growth in cells like with Lymphocystis and Lymphosarcoma. Certain chemicals are also known to be carcinogenic and may cause tumors. Tumors on the skin are very obvious and some resolve itself over time, given an increase in temperature and optimal water conditions.

Last Updated on Monday, 09 November 2015 22:14


Gas Bubble Disease

The condition of gas bubble disease is very similar to the “bends” which divers experience when they rise from deep water to the surface too quickly. The rapid change in pressure results in tiny bubbles forming in the blood, body cavities, tissues and skin layers of fish. This “disease” is caused by super saturation of pond water with dissolved gases. It occurs under various conditions. The first is where cold water that is already saturated with gas, flow into a pond where it may be heated without adequate time or aeration for volatilization of excess gas. It also commonly results when water from deep wells, often high in nitrogen gas and carbon dioxide, is brought into an aquaculture facility without proper aeration. It can also be caused in small pools by leaving a garden hose running on the bottom of the tank. The water in the water reticulation system is under tremendous pressure and once the hose is submerged, there is no release of excess gas to the atmosphere, resulting in super saturation of pond water and the resultant complications. Gas bubble disease can also occur where a small leak exists before the pump inlet of a pressurised system. It has also been associated with faulty pumps and, although rare in ponds, the presence of heavy algal blooms when high levels of oxygen are released into the water during photosynthesis.

As water, which is supersaturated with nitrogen and oxygen gasses, passes over the koi’s gills, high levels of gas enter the bloodstream. Once these gasses are in the koi’s bloodstream, a change in pressure result in these gasses to come out of solution and form tiny bubbles in the blood. These bubbles are known as embolisms. Nitrogen bubbles in the blood can block blood vessels and severely affect the circulation. This may result in abnormal behaviour, erratic swimming and even death. I have witnessed stress induced reddening of the skin, especially the fins, minutes before they succumb.

Last Updated on Tuesday, 11 November 2008 16:09