Fish Disease Diagnosis
Fish Disease Treatments
Ponds, Aquaria & Filtration

Koi Overview

Koi are often aptly named "living jewels" because of their exquisite markings and patterns. They are lovable aquatic animals, each with its own personality and quirks. However, because of; usually high stocking densities in often barren ponds, koi keeping can be demanding. A degree of skill and expertise is required to maintain optimum conditions and prevent diseases. 

Myths & fallacies

If you ask six people the same question about diseases or treatments you will get six different answers. Sorting out the facts from the fallacies can be tricky!

Koi keeping skills

Don't run before you can walk. The problem with learning the hard way is that it is usually the fish that pays the price!

Koi-keeping equipment

Water-testing kits, nets, first-aid. Are you ready for problems and emergencies?

Ponds & the nitrogen cycle

Without the nitrogen cycle, koi would slowly poison themselves - find out about this important topic.

Pond filtration

At the heart of a pond is the filtration system. An introduction to koi pond filtration

Disease & diagnosis

When health problems strike, an early, accurate diagnosis  is the most important first step.

Bacterial infections

Why do bacterial infections, such as ulcers and fin rot, affect fish and what are the best ways to treat them effectively?

Gill - structure, function & disease

The gill is the equivalent of the human lung - any chemical or physical damage will have a severe effect on fish health.

Parasites & fungus

Have the fish gotten parasites because they are ill - or are the ill because they have got parasites? What is the fish fungus hiding?

Miscellaneous problems

Koi suffer can suffer from a whole range of health problems and diseases including hypoxia, gas bubble disease, dropsy and general lumps and bumps. more... 

Disease treatments

Often the biggest threat to health are fish "medications" How do most of them work? Should you treat the pond or the fish? 

I am often asked about stocking levels. This really depends on so many factors - not least of all the skill and experience of the pond-keeper!  However, it is important to realise that as stocking levels increase, the safety margin between good and poor health and conditions decreases.

As densities increase, so does the need for constant water-testing, health monitoring and system maintenance. It is these considerations along with initial pond and filter design that really determine how many fish you can keep. As a very general guide, a safe (ish) stocking level would be around 8-12ft of fish per 1000 gallons (UK 4,500 litres) - assuming adequate filtration etc.  Once you go over this level you start to move into "intensive" stocking levels!

"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.


Module Subart1

MOdule Subart2

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

VISIT:  h t t p s : / / f i s h t r e a t m e n t s . c o m

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