You can’t find potassium permanganate (PP) on the shelves of your local fish store or online fish catalog. This purple crystal, which is used by discus hobbyists to kill bacteria, external pests, like gill flukes and reduce the bio-load in fish tanks can be found at stores that sell home water softener equipment. I purchased mine at Sears. Potassium Permanganate and its antidote Hydrogen Peroxide Most hobbyists’ only need a small amount of potassium permanganate like the 6 oz. Bottle pictured above. Hydrogen Peroxide (HP) should always be kept on hand when using PP. It is an antidote and can be added to the tank if the fish are in distress from the PP treatment. I add it to the tank to neutralize the PP at the end of the 4-hour treatment. Hydrogen peroxide can be found in grocery and drug stores everywhere. To make the stock solution pictured above I used a clean pint bottle filled with tap water and added 1/8 teaspoon of the potassium permanganate crystals. This solution can be stored in a cool dark cupboard for several months. Four Hour Tank Treatment. I leave the empty filter running on the tank and cycle the PP through it. This cleans the filter housing and aerates the tank during treatment. Wipe down walls and floor of tank. Wipe off the heater, cords, airline tubing and any decorations in the tank. Add 4 ml of the stock solution per gallon of aquarium water. Another way to measure is 5 tablespoons per TEN gallons of aquarium water. You want the water to turn a rich purple color and keep that color for the full four hours. If the water turns rusty, tan or orangey the PP has stopped working. At the end of four hours I add 3% Hydrogen Peroxide one capful at a time until the water turns clear. Wait a couple of minutes for the hydrogen peroxide to work before adding more. A more accurate way to measure is to add 5 ml per 20 gallons of tank water. Then I do a 50% water change vacuuming the bottom thoroughly. Don’t forget to rinse the filter media in de-chlorinated water before returning it to the filter. Treatment can be repeated in one week if needed.
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