Potassium permanganate - How to use

It is a general misconception that potassium permanganate is dangerous to use for fish.

One vet would warn "very strong and dangerous...it burns the gills and we do not recommend" while another vet cannot stop singing its praise as "extremely effective".

What the normal koi keeper hears is "don't use it...it is dangerous"

In fact it is just the opposite.

If used correctly, it is perfectly save for your fish and a good alternative to other, more expensive, treatments.


Potassium permanganate crystals (or other proprietary ready-for-use solution) is a very effective treatment for a wide range of parasites, bacteria and fungus.

What you should hear: 

Parasites: Flukes (both Dactylogyrus and Gyrodactylus), Trichodina, Costia, Chilodonella, Epistyles etc. You would probably use salt for the last three and hope for the best.

Bacteria: Columnaris (Flavobacterium), Aeromonas, Pseudomonas, Edwardsiella, etc.

Other: Saprolegnia (fungi), alga and Hirudinae (snails).

Not toxic to plants and used as a disinfectant for newly purchased plants. Both roots and leaves. Also as a dip for newly acquired fish.

(This same treatment regime can be followed on your own skin. Feet does well with it.)


Treatment attacks also infected and necrotic tissue and therefore gills, ulcers and ALL areas with bacterial or parasitic infections are affected. Brown manganese oxide form complexes with molecules in the process. This brownness is often interpreted as “burns” which it is not. At the right dosage and exposure it will not affect healthy skin of the fish.

This is slightly less impermeable for oxygen than the diseased tissue, therefore ANY stress exhibited by the fish should be reason to terminate the treatment (with hydrogen peroxide)

Even such, terminated treatment will be beter than most other treatment and real improvement can be seen if repeated a number of times en second or third day.

It can be said that potassium permanganate has the tendense to ‘cut’ to the root cause of the infection by first removing the secondary infection or dead cells, and then deactivate that infection itself. Giving antibiotics at the same time creates a two-pronged attack (from the inside.)


Pond treatment for parasites and snails: 2-4 g / 1000 liters.
Keep on adding in small doses of 2g/1000 litre to keep the pond water pink for 1-2 hours 

Pond treatment for bacteria and ulcers: 2-4 g /1000 liter
Keep on adding in small doses 2g/1000 litre to keep the pond water pink for 8-10 hours 

Dip:  very effective for parasites, bacteria, ulcerations etc. Use 1 gram per 10 liter water for 7 minutes. Always aerate and ALWAYS remove the fish if it gets restless and jumpy. Control timing precisely and do not treat too many fish at the same time unless you can time the treatment of each fish correctly.

This treatment tough, can push an ailing fish ‘over the edge’. Therefore fish already weakened by disease should first be treated with a 30-50% dose first time. Alternatively simply shorten you dipping to 1-2 minutes if the gills are infected and necrotic.

Important. Always de-clog the gills with a Peroxide (hydrogen peroxide) treatment to the pond. It not only terminate the action of the potassium permanganate, but will clear the water from the brown colour. Will also aid in removing the brown coloured necrotic tissue from the gills.



I want to warn about use with salt. Salt (NaCl) is additive to potassium permanganate. To strip parasites from basically HEALTHY FISH can be tolerated, but sick, weakened fish should never be subjected to such treatment and will surely die. Always test salt level or ask the pond owner about his salt regimen before deciding on the protocol for the potassium permanganate treatment.

For certain phenotypes of the Doitsu koi the uptake of oxygen is poorer for certain physiological reasons. They stress more quickly and die due to oxygen starvation. Use half the recommended dose/time when dipping the first time at least to determine their suitability for the treatment..


Like ALL chemicals used for treating fish it is toxic and dangerous if overdosed. Always weigh the required dose and do not just estimate. (You might think you are good at this, but one mistake and you can lose your collection) Always first dissolve the required quantity completely in bucket before application. Protect yourself from the dust and spills of strong solutions as standard precaution. It can cause caustic burns easily at high concentrations.

For this reason it is easier and more safe to use proprietary solutions for fish treatment. (although a little more expensive)


Since potassium permanganate is bactericidal, it will over time kill most bacteria in the pond if the dose is long enough. Free floating organisms first, but those forming a biofilm will be more resistant, go in stasis or will die last. So yes, it will ‘knock’ the biological filter. If pond is treated for 1-2 hours (pink) and you terminate treatment (with Peroxide), the parasites and some bacteria will be dead, but the hardly will not be affected. If you threat for 8-10 hours (pink) the biological filter will take a serious knock and take some time to recover. Do not feed the fish until you are sure the filter is working normally (by testing for ammonia and nitrite)

Bypassing the biological filter is always advised while oxygenating the pond. It is also good practice to leave the flow of the pink fluid flow for the first 30-60 minutes through the filter, but beyond that, bypass the filter.

Servaas de Kock
24/12/2013 and updated since

(Be on the lookout for other articles on this subject)