Postassium Permanganate (PP)

Potassium permanganate is an oxidizer which can be used to "disinfect" the external surfaces of fish. It effectively removes most external parasites, as well as fungal and bacterial agents. Most fish can be treated by prolonged immersion in a 2 mg/L potassium permanganate solution (water must retain a purple color for at least 4 hours), although some species (i.e., Malawi cichlids) seem to be sensitive to it and may not tolerate a full strength (2 mg/L) bath. Because of its harsh oxidizing properties, potassium permanganate should not be applied to fish more frequently than once per week or mortality may result. It is safe to use in marine and recirculating systems at 2 mg/L.

Treatment Failure
Poor efficacy following use of potassium permanganate is usually caused by one of three factors:
(1) incorrect or incomplete diagnosis;
(2) incorrect calculation or measurement of amount of chemical needed; and
(3) excessive organic material in the system resulting in rapid degradation of the chemical.

Determining the Amount of Potassium Permanganate to Use

To calculate the amount of chemical required, a simple formula can be used:

Amount of Chemical = Volume x Conversion Factor x Treatment Rate

If the pond or tank volume is measured in gallons, the conversion factor is 0.0038 and the answer will be given in grams (see Table 1 for other conversion factors). For a treatment rate of 2 mg/L, this formula would be:

Grams of Chemical = Gallons Treated x 0.0038 x 2 mg/L

Therefore, to treat a 250-gallon vat, the grams of potassium permanganate needed are:

Grams needed = (250 gal) x (0.0038) x (2 mg/L) = 1.9 grams


An inexpensive gram scale can be obtained by purchasing a dietary scale at your local grocery store or pharmacy. One level teaspoon of potassium permanganate weighs about 7.0 grams

Reference source: Simplydiscus.com