What is it

Potassium permanganate (PP) is a compound that is used by aquarists for the disinfecting of plants or ornaments before placement into aquariums. It is used to remove organic build-up in tank water, and kill bacteria and fungi. It is also employed to treat most parasites that infect fish.

Potassium permanganate is the chemical compound KMnO4. The salt is also known as "permanganate of potash" and "Condy's crystals". The permanganate ion is a strong oxidizing agent. It dissolves in water to give deep purple/pink solutions, evaporation of which gives prismatic purple-black glistening crystals (see picture below).

TIP: To aid accurate dosage, a stock solution of one gram per litre of clean water (preferably distilled or de-ionized water) could be used, giving 1 mg potassium permanganate per ml of water.
TIP: Potassium permanganate rapidly loses its potency when exposed to light and air. So keep any solution you make up well away from light and in a airtight container. Ensure you clearly mark any such container as poison and keep it well away from children. Dispose of carefully after 2–3 months.

Plant disinfecting

To prepare for the disinfecting of aquatic plants, prepare 1 Litres (0.3US G.) of lukewarm (25°C (77°F) ) clean tap water and drop 10 mg of crystals into it and stir until the solution turns deep blue/purple.

Be careful as this solution will stain

Dip the leaves of the plant into the solution for 10 minutes, being careful not to dip the roots of the plant in it.

Then rinse off thoroughly.

This will kill live snails as well as snail eggs and parasites

Fish treatment

Potassium permanganate can be used to treat parasites on individual fish. It will eliminate anchor worms, fish lice, flukes, ich, costia, cotton mouth, fungus and most types of bacteria. Prepare 8 Litres (2.1US G.) of water at aquarium temperature and add 1/8 teaspoon (0.6g) of crystals.

Stir until dissolved.
Dip fish into solution for 5 minutes. If fish looks stressed, remove at once.
Dip fish into clean water for a few seconds to rinse.
Do NOT use this level of potassium permanganate in an aquarium tank!

Tank treatment

Potassium permanganate is an effective anti-parasite treatment (Ich, etc.), as well as being able to remove odours from tanks and increasing the redox potential of the water.

However as this compound is strong, using the wrong dosage can result in poisoning the fish.

Biological filtration systems should be removed before applying.
This compound works best with little or no light.
Typically used against bacteria (including your nitrifying bacteria in your filter) and parasites. You use a solution of 2ppm (this is 0.5 grams per 380L (100 US gallons) or 0.065g per 50L). Repeated every 2–3 days for a maximum of 5 treatments