Fish disease diagnosis

Fish disease treatments

Koi ponds, aquaria & filtration



Freshwater fish


Help page

Sources of help and advice when problems strike

Important links

It is important to realise that it is impossible to make a definitive diagnosis without seeing the fish and checking the system. At best, one can make an educated guess - but the accuracy of this depends very much on the information available.

To simply say; "my fish are unwell; what's wrong and what do I do?" is obviously of no help at all. (Try saying dog instead of fish!). The FishDoc site doesn't set out to provide an 'instant' diagnosis service.

The purpose of the site is to provide a source of authoritative information and advice for fish keepers who are interested in finding out how to tackle fish health problems in a  methodical and professional manner. The following pages and related links provide most of the basic information needed and are essential reading BEFORE making a diagnosis or carrying out treatments.

Clinical signs or symptoms of disease

Comprehensive guide to common disease 'symptoms'.  Although it isn't possible to make a definite disease diagnosis based solely on 'symptoms' or behaviour, this guide helps to narrow down possible causes and indicates what further examinations and tests are required


Diagnosing fish disease

Fish disease is a complex subject and it is important that any health problems are accurately diagnosed. Follow the step by step health workup and make sure that you don't miss any obvious pointers

Parasites - an overview

Parasites are a common problem, often predisposing the fish to bacterial infections.  Find out more about these 'nasties' and why they pose such a threat in the confines of a pond or aquarium


Basic steps in treating health problems

A guide to diagnosing and treating health problems and steps to take when it is not possible to make a full diagnosis


Fin rot and ulcers

Bacterial disease is often a major problem. Find out about antibiotic injections medicated food and baths. How to clean an ulcer and use topical treatments. With proper treatment, bacterial problems can be resolved in 2-3 weeks with over 90% survival rate. 

Using your microscope

It is impossible to make a full and accurate diagnosis of fish disease without using a microscope - it really is a basic but essential part of disease diagnosis. Follow this guide to buying and using a 'scope - including skin and gill scrapes.

New Pond / tank filter start-up

New pond / tank syndrome is a common problem leading to fish losses from ammonia and nitrite poisoning. Find out how to manage water during this vital phase


There are many procedures that need a fish to be anaesthetized. Find out how to safely anaesthetize a fish.  When a disease problem can't be resolved, sometimes euthanasia is the kindest option.


I should stress, unless you are comfortable about diagnosing fish disease and deciding on a treatment plan, you really should seek professional help from either an aquatic health expert or fish-friendly vet. After all, you wouldn't expect to be able to fix the family car without some knowledge of what goes on under the bonnet and a basic tool-kit!  Would you? 


Fishdoc would like to thank the following benefactors for their sponsorship of this site: - Sho Koi - Aquadyne Bead Filtration - - Koizyme (Genesyz Aeromonas Fighter

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