Fish Disease Diagnosis
Fish Disease Treatments
Ponds, Aquaria & Filtration

Welcome to the case history files.

These are just a sample of everyday fish disease cases that I become involved with. I guess most of us read plenty of books and magazines about aquatic health and fish keeping and somehow the problems, scenarios and often the clinical disease signs they describe never quite match our own situation. It's almost as if everybody else suffers from different problems to us, or our diseases are impossible to cure without heavy losses.

NuFlor Scald

Nuflor scald may be seen in the base-white Koi about five days after injection. There are five things which seem to help. Do NOT use NuFlor unless this rare complication is acceptable as a possible consequence.

White spot, Argulus & Chilodonella

Affecting 4,500 gallon (UK) koi pond. 9 koi died after mouth fungus was wrongly "diagnosed" (April 2000)

Koi bacterial ulcer 

The fish kept recovering but now it is laying on the bottom.  (April 2000)

Goldfish killers

These were not your normal pond killers! (May 2000)

Fish disease is a complex subject

Part of the problem is that there is a tendency to oversimplify what is after all a complex subject, dealing as it does with animal health, water chemistry, biology, anatomy, animal physiology etc. Unfortunately, a lot of very important stuff often gets lost in this oversimplification and people often lose sight of the reasons why most diseases happen and how to spot fish disease at an early stage. 

This is partly due to lack of experience, but also encouraged by the raft of myths and fallacies surrounding many aspects of fish keeping, which often lead to fish keepers becoming total confused and bewildered by all the conflicting advice they receive. 

A big-time problem with resolving fish disease is the continuing belief that you can diagnose fish disease by simply hearing a description of the fish behaviour or physical change - or by a cursory glance into the pond or tank. No matter what the experience of the person concerned - at best this can only be a guess and not a diagnosis. My own experience is these guesses are very often wrong.  If the guess is wrong, then it follows that the treatment will be wrong and the losers will be the fish.

Fish disease case histories

So, to put a more practical spin on the subject I will be describing and detailing a sample of cases that are relevant to a particular aspect of fish health - be it water quality, disease diagnosis or treatment. In the majority of cases you will see how problems could have been avoided.

I will, wherever possible include photos, but this isn't always possible.

"Koi Health & Disease" by Dr. Erik Johnson DVM is 200+ pages from Fish Health Practice - Readable by Beginners and delivered overnight from

Fish disease problems? Need some help? The help pages take you through the basics of the 'fish health work-up' diagnosis method and basic fish disease treatment methods.

90% of all health problems and fish deaths are caused by poor fish keeping! The key pages are essential reading for all beginners and intermediates who are serious about disease prevention.


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What if you could just get "Here's what to treat with." and no advice or education?

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Expanded Content by Dr. Erik Johnson, and Used with Permission; Frank Prince-Iles ©2009 All Rights Reserved