Pond Potassium Permanganate – Is it Safe? (Treatment Guide)

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Potassium Permanganate – Is it Safe for Koi & Goldfish? (Treatment, Dosage & Uses)

Potassium permanganate that has been formulated for koi pondsPotassium permanganate is a water soluble, extremely oxidative compound derived from manganese. Historically, it has been utilized to treat drinking water and wastewater around the world since 1913, as it aids in removing bacteria, pathogens, iron, algae, and other potential aquatic evildoers simply via its oxidation process as it reacts with water.

For these reasons, potassium permanganate is also somewhat commonly used in ponds to promote healthy water quality and reduce or eliminate some types of fish diseases, parasites, and pathogens. At higher doses, it has also been used to kill off invasive zebra mussels from natural bodies of freshwater.

How Does Potassium Permangante Work?

As an incredibly reactive substance, potassium permanganate will respond to any organic matter that is present. Once placed in water, the compound works by oxidizing until only permanganate ions and manganese dioxide are left. The permanganate ions are destructive to living tissue, and works by breaking down the cell walls of parasites, algae, bacteria, and any particulate organic matter that they encounter.

Potassium permanganate at different stages of oxidation
Initially potassium permanganate will be a deeper purple, but during oxidation the compound will slowly turn a lighter pink. Public domain.

The amount of organic matter present in the water as well as the dosage of the compound determines how long that the potassium permanganate will remain active in the water. You will be able to tell when the chemical is working based on the color of the water – at first, water may turn a purple color as the crystals dissolve. During oxidation, water will become pink and then change to a yellowish hue as the crystals become inactive. After a couple of days, the water should return to its normal color.

Outside of ponds and drinking water, potassium permanganate is also prescribed by doctors at very low doses (typically a concentration of .1% or less) to treat various skin ailments such as eczema, fungal and bacterial infections, and to treat wounds that are infected.

What Can Potassium Permanganate Treat?

In aquaculture, potassium permanganate is used to treat a variety of fish ailments with varying effectiveness via dissolving crystals of the compound in water. It is important to note that it’s not viricidal, so it won’t do anything to combat viral infections. Even more important to note is that potassium permanganate can cause skin damage if too high of a dose is used or if it is used too frequently.

1) Parasites

Trichodina, Costia, and Chilodonella are all potentially deadly protozoan parasites that potassium permanganate can help to kill off. Some flukes, which can invade the nervous system if left unchecked long enough, are able to be treated with potassium permanganate. These include the species Gyrodactylus and Dactylogyrus. Ich and trichodiniasis, both caused by ectoparasites, are also readily treated by potassium permanganate due to its highly oxidative nature.

2) Bacterial Infections

Bacterial gill disease is, as you might expect, a bacterial infection of the gills that results in painful spots, swelling, discoloration, and potential necrosis of tissue. Potassium permanganate likely won’t kill all of the bacteria, but it will give your fish enough relief to allow it to start the healing process. You should take other steps to improving water quality to prevent a resurgence of the bacteria, such as salt baths, draining and cleaning your pond, and ensuring that your fish aren’t overcrowded.

3) Fungal Infections

potassium permanganate can help with koi fungus
Potassium permanganate can help with fungal infections, but should be used carefully. Public domain.

External fungal infections are killed off usually within one or two potassium permanganate baths. However, as mentioned throughout this article, potassium permanganate can be toxic and volatile if used improperly, so should only be resorted to for particularly stubborn or more severe fungal infections that more traditional methods aren’t able to treat.

4) Ulcers & Certain Diseases

Aeromoniasis, also known as ulcer disease, involves skin lesions and ulcers that often become infected and as such have a difficult time healing on their own. Columnaris disease as well as aeromoniasis both involve bacterial infections that evolve into these diseases, with columnaris spreading to the entire body if left untreated. Specifically, studies have found potassium permanganate to be effective in reducing the presence of columnaris species by as much as 70%.

Is Potassium Permanganate Safe For Fish & Plants?

Pond aerators help keep water flowing and healthy during potassium permanganate treatment
Aerators will increase dissolved oxygen and help fish feel comfortable during treatments.

Potassium permanganate has the potential to be toxic if used incorrectly, such as improper dosage or using it in a high pH environment. Since it reacts with any and all organic matter, it can burn your fish’s gills and is also deadly to aquatic plants. Therefore, potassium permanganate is best used in a quarantined environment with no plants and minimum other organic matter.

When used appropriately (that is, pond volume is measured and the product label is followed so as to obtain proper dosage amount and duration), potassium permanganate is considered a safe compound for use with fish. It should be noted that the compound, contrary to popular belief, can actually temporarily decrease the amount of dissolved oxygen in the water as it will also kill off algae and other organic oxygen producers, so running an aerator or air pump can help keep fish happy during treatment.

Considerations When Using Potassium Permanganate

When using this product, make absolutely certain that none of it is able to get into the natural environment. Keep containers properly stored away, and ensure that any quarantine tanks or ponds are not going to overflow from rain or any other event. Any product that winds up in the soil or, most notably, natural waterways, will cause significant ecological harm!

Goldfish and koi are tolerant of potassium permanganate, though most fish and plants are not
Potassium permanganate is toxic to aquatic plants and certain fish species, but both goldfish and koi can to tolerate it. Public domain.

Potassium permanganate should not be mixed with other pond treatments. In particular, if used in conjunction with formalin, the two compounds can have an explosive reaction. Do not use in tandem with salt treatments, either, as potassium permanganate becomes more toxic with increased salinity.

Cichlids in particular have been found to be sensitive to potassium permanganate, so it’s best to avoid use of the chemical with these subtropical freshwater fish. Zebrafish as well as certain catfish species (in particular, the African catfish) are also quite sensitive to potassium permanganate, while goldfish are quite hardy and studies have found them to be quite tolerant of the compound. This is by no means an exhaustive list, so be sure to thoroughly conduct your own research prior to use to ensure that potassium permanganate is safe for the fish species present in your pond.

Potassium Permanganate Guidelines & Mixing

Changing pond water before a potassium permanganate treatment
If you dose within your pond instead of a quarantine tank, a heavy water change is recommended before and after treatment. Public domain.

Due to its high reactivity with organic matter, potassium permanganate can be mixed in distilled water prior to adding it to your pond. If mixed into a container of regular water before being added to your pond, any organic matter present in the water will use up much of the potassium permanganate’s oxidative power before it even has a chance to come into contact with any parasites, bacteria, or fungus that are impacting your fish.

If you choose to use the treatment in your pond rather than in a quarantine tank, it is advised that you perform a 50% water change to reduce the amount of organic matter that is present in your pond.

In addition, do not use this compound if you have high pH water – the greater the pH, the more toxic that the compound becomes to your fish and even plants. This same concept applies to salinity – potassium permanganate should only be used in fresh water. In addition, make certain that you do not treat your fish more often than once per week, as doing so can cause death.

Dosing Potassium Permangante – How Much Is Too Much?

As a general rule of thumb, a dosage of 1-2 milligrams per liter of water that is present in your tank or pond should be sufficient to clear up the ailments listed earlier in the article. It is not generally recommended to exceed a dosage of 2 mg/L, as this seems to be the concentration at which potassium permanganate can become toxic to some fish species. This can concentration can be mixed in distilled water and then poured into your pond or, preferably, a quarantine tank. It will dissipate on its own.

For a quicker solution or more serious fish ailments, you can use up to 10 mg/L for a ten minute tank bath or dip. While some sources say that you can leave fish in this concentration for as long as an hour, this appears to be the chosen treatment method/time in some fish hatcheries with a large number of fish and is not recommended for backyard ponds or quarantine tanks. Again, do not repeat either of these treatment types more often than once per week else your fish may suffer serious damage to the skin and gills, or potentially die.


7 thoughts on “Pond Potassium Permanganate – Is it Safe? (Treatment Guide)”

  1. When treating your pain with the product above is it safe for your cats and dogs to go to the pond and drink out of it why it’s being treated there’s nothing on the bottle I understand it gets put in humans medicine here in there but I just need to know thank you have a nice day

    • Hi Dori,

      I would try to keep your cats and dogs away from the pond for a couple of days after treatment if you treat the pond directly. It’s recommended that treatment occur in a quarantined environment – so if you’re treating your fish for bacteria or parasites, we recommend quarantining them in a separate tank and treating just the tank rather than the entire pond, if possible, to avoid any potential toxicity to any other plants or organisms in the pond. This would also eliminate the need to keep other pets away from the pond.

      Hope this helps!

  2. great resource article thank you for the effort putting this together. you might mention that you can neutralize the KMnO₄ using hydrogen peroxide.H2O2. from my experience, this is a good measure when disinfecting tubs ponds or outdoor tanks. let the permanganate work then neutralize it to make sure the reactions are finished before draining.


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