Fish disease diagnosis

Fish disease treatments

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Freshwater fish


Fish disease treatments

treatments home page

Fish disease treatments should be straightforward provided that the problem has been accurately diagnosed at an early stage. However, it is very important to bear in mind that many fish are killed every year by the improper use of  medications. 

Disease treatments

an overview of how treatments work, why they often don't work and why they sometimes kill fish.

Disease treatment basics

When you have fish health problems, this guide details the steps to take, and what to do if it isn't possible to make a definitive diagnosis.


are an important treatment option against bacterial diseases if they are used properly.

Injecting antibiotics

gives the best results against bacterial infections  - especially when dealing with severe cases.

Antibiotic baths

and dips are not generally as effective as antibiotics given by injection. Baths and dips may however, be useful for surface infections.


Effective treatment against anchor worm (Lernaea) and possibly fish lice (Argulus)

Medicated food

is a useful option for treating bacterial disease, but it does have some disadvantages.

Topical treatments

can be very effective against bacterial diseases - especially when used in conjunction with antibiotics


Can be tricky to use - but is effective against some parasites - it can also assist in gill problems. 


  a  treatment for marine parasites.

Malachite green and formalin

an all-round anti-parasite treatment, especially good for white spot. 


the "bad boy" of treatments - but the best treatment for the "difficult" parasites such as Argulus.

Potassium permanganate

an effective treatment against many parasites, especially Trichodina. Can be useful for bacterial problems and disinfecting nets etc. 

Quaternary ammonium compounds: (QACs)

useful for gill disease - as it acts as a mild disinfectant with detergent action to remove debris.


The fish keeper's standby for parasites, gill congestion and osmoregulation problems. It's safe, and cheap

Using  "medications"

  • If possible, make a definite diagnosis rather than a presumption or guess.  This enables specific targeting of both the problem and cause. Follow the diagnosis guide

  • Check, double check and get someone else to check if you are not 100% sure of the volume of the pond or tank.

  • If there are signs of distress remove the "patients" or rapidly dilute the treated water

  • It is always advisable to carry out a follow-up examination to ensure the effectiveness of the medication and if necessary switch to another.


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