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Case studies

Secondary Hi Removal

The practice of effecting cosmetic changes to animals is a much talked about subject and not everyone agrees with it. Amongst the koi fraternity cosmetic changes are made globally and most notably, by some of the most prominent breeders in Japan. For the hobbyist it is a personal choice. Given the fact that a hobbyist can only accommodate a limited number of fish during his lifetime and relatively few Tosai that he/she has carefully selected, will retain the specific attributes that led to the selection in the first place, decisions about cosmetic changes must sometimes be made. There are few options available to the hobbyist. Should the fish that has been raised and cared for be destroyed or passed on to someone else, while the chances are very good that the next selected fish will develop some other more serious defect?  It is also a known fact that no koi is perfect. So how many times should the hobbyist select a fish and then get rid of it?

Last Updated on Wednesday, 16 November 2011 09:47


Beni Kumonryu with Tumour


Introduction is copied from the tumour Article


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, 14 March 2011 22:26





I am convinced that most koi hobbyist has seen dropsy symptoms in fish. I am further convinced that a large percentage of hobbyists that have noticed these symptoms initially thought the fish is overweight, laden with eggs etc. I am also sure that the initial humorous reference to “our pregnant fish” turned to alarm with the rapid expansion of the abdomen and severely bloated appearance. Most owners realize that something is seriously wrong when pop-eye develop. A few days later when the internal pressure causes the scales to protrude from the body, the alarm turns to dread. Dropsy is arguably the most feared and common "disease" of the pond.  The reason is that unless dropsy is caught in the very early stages, a cure is almost impossible. The above statements are based on the numerous calls that I have received over the years, only to arrive at a pond and having the difficult task of convincing the owners that treatment will serve no purpose. I have also attempted to treat such fish when the owners insisted. Unfortunately the treatments were without any success because in advanced stages, after the body has swelled, the eyes have bulged and/or scales are sticking out (like a pinecone) this disease is usually always fatal.

Last Updated on Thursday, 05 August 2010 21:19


Crouching Tiger


Over the years I have had many puzzling experiences with Koi. The first thing that comes to mind is the six Koi that survived under horrific circumstances for months when a house was on sale. There were no pumps running and no maintenance. It took the new owner weeks to give attention to the neglected pond. After removing a few plastic chairs, old bird cage etc, he saw movement! Today the six Koi are still in the now well maintained pond and doing well.

Then the question springs to mind: Why don’t a dedicated Koi keeper like a friend of mine in Richards Bay have the same luck with a pristine pond of 50 000 litres? In this instance it took us two weeks of agony and still we could not save his precious collection of Koi. A silent stalker was lurking but we could not identify it! This big pond is equipped with four bottom drains, a settlement chamber, large filter and UV. The turnover rate is at least once every 90 minutes. In the last filter chamber was a platform, supporting various plants, but mainly water iris.  Water is returned to the pond via two aim flows and a small water-curtain, 35 cm wide and about 40 cm high.

On the property is also a quarantine pond, fully equipped.

How it all started....


Last Updated on Tuesday, 07 September 2010 20:46


Kinked Back


Lately I came upon quite a few instances of this kinked back phenomenon. Normally it is one fish per pond and the owners are baffled by this overnight occurrence. Careful detective work is necessary to determine the cause. There are various reasons for pond fish to develop a kinked back and all possible causes should be considered before appropriate action can be implemented, even if it just to ensure the safety of the rest of the collection. Kinked back/scoliosis is caused by a variety of causes, none of which is infectious. Normally, the reasons, for kinked back/scoliosis are one or a combination of the following:

Last Updated on Thursday, 01 July 2010 09:45


Post mortem: Systemic Bacterial infection

On 18 November 2008 a client called with the news that one of his fish died during the night. The fish did not show abnormal behaviour that indicated a potential problem (Maybe he did not notice?). Upon arrival at the pond we followed the normal routine to determine the cause of the fatality. The filter system was clean and we found no sign of accumulated debris. The water parameters tested fine and a skin scrape revealed no parasites.

The purpose of this article is to give the hobbyist some insight into the devastating effects of bacterial infection once it has penetrated the defence systems of a fish. It is also intended to show why systemic infection (septicaemia) is almost incurable because of the massive damage to the internal organs. Some bacterial infections may develop over time and the fish will display bloating (Dropsy, pine cone disease) because the osmoregularory system is compromised. In other cases, the fish is substantially normal and dies suddenly.

Last Updated on Thursday, 22 January 2009 22:58


Kohaku with severe lymphocystis


August 18, 2008
I received a call from a friend who informed me about his 48 cm, very tame doitsu kohaku with a strange growth inside the mouth, just behind the upper lip.  Upon close inspection it was clear that the lymphocystis virus was responsible for the wart-like growth, almost the size of a marble.  The whole upper lip was also covered with smaller growths.  What was disturbing was the fact that the fish was unable to eat properly and because of the constant nibbling on algae on the side of the pond, the growth has become tender with clear signs of infection.  The skin also exhibited tell-tale red streaks, indicating that the infection may become systemic.  A scrape revealed no parasites

The owner of the fish was advised that lymphocystis is a virus and could not be cured with the normal antibacterial medication normally used for treating koi.  Lymphocystis could only be cured through the immune system, and normally disappears during the second summer after infection.  In this case, however, there was a real danger that the fish would not survive because of its inability to eat as well as the danger of infection and frequent injections.

Last Updated on Wednesday, 18 August 2010 10:07