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You Need to Know about Potassium Permanganate

I was forwarded a link to advice on how to use Potassium Permanganate (PP) in an aquaponic system which suggested the use of 1/4 of a teaspoon in 400 liters of water.  Unfortunately, not a very accurate or safe way of using PP.  PP is a very strong oxidizer which is toxic to your fish and plants.  PP is non selective with bacteria and will inhibit your bio-filtration, in some cases completely. [heading] Potassium Permanganate Use at Your Own Risk [/heading] It is very important to consider if you really need to use it as a treatment in your aquaculture or your aquaponic system at home.  In Aquaculture, a minor use permit is required for its use, but salt has the same requirement.  I can not see any point you would need to use PP at home providing your have good filtration, low stocking density and perhaps maintain salt levels at 1 to 2grams per litre. If you decide that you want to use PP for treating columnaris (Flavobacterium columnare) a common bacterial disease, first you must be sure your fish have a problem which potassium permanganate can fix.  Usually by time the hobbyist knows there is a problem, it will be too late to treat with Potassium Permanganate. Generally, following a treatment most will not have the tools (microscope) to determine the treatment has been successful and if the disease has become systemic PP may not be a suitable treatment.  I emphasise seriously consider if you really need to use it. Attached is a useful white paper addressing some of the issues with PP use in Aquaculture. I strongly suggest you adopt a precautionary approach to the use of Potassium Permanganate in your system and should you use it, take some time to conduct a short PP demand test to estimate reasonably accurately the amount you will need to use in your system.  General “rules of thumb” in literature suggest an average concentration of 2mg/L and no more than 6 to 8mg/L.  These do not account for the organic demand. However some fish species are more sensitive to PP than others (Tilapia Juveniles 1.8mg/L exposure results in mass mortality) and because PP is an oxidiser it will react with the organic solids in your system I advise you test how much you need with your own water and avoid general advice that may not suit your situation. Not many people have capacity to diagnose a disease in fish from a photo over the Internet as most of them require lab testing and by the time the disease is visible to the eye it will often be associated with a secondary infection.  So please be cautious with advice from Internet photos about what disease your fish might have and what treatment might work at an ambiguous and dangerous dosage. I will advise you seek a veterinarian or uni lab to assist with accurate diagnosis and treatment advice, keeping in mind diseases in fish are reportable to fisheries to help them keep track of outbreaks and risks to commercial producers and local ecology.   Fisheries may be your first stop in seeking advise, should you suspect a disease in your fish. As we know all diseases in aquatic systems are generally environmentally driven and often from elevated volatile organic solids, poor water quality and management and poor handling of fish.  While a treatment may reduce the severity of loss, prevention as they say is better than the cure.  For those that plan to use Potassium Permanganate here are some tips on determining how much to use. One thing to consider in an aquaponic system is PP oxidises Iron and Manganese.  This means the use of PP, while might add a very small amount of potassium  (PP is only 25% K by Molar weight and we are using milligrams of it there will be no benefit to your plants), it will remove Iron and Manganese, so you may need to introduce these after treatment. Safety First PP is a chemical with strong oxidising properties and needs to be handled as such.  Do not mix it with anything else. Contact with your eyes will be excruciating to say the least, wear eye protection It will cause skin irritation as all oxidisers do, so gloves are very handy Because PP is reasonable good at killing bacteria and we are 90% bacterial cell mass and 10% human, don’t ingest it or you will die. PP will stain anything permanently, your cloths, hands and anything it comes in contact with. [heading] Potassium Permanganate Demand Test [/heading]A PP demand test, tells us how much of the PP will be used up by the organics in our system.  Then we add on top of that our actual treatment dose. We are going to make up a stock solution because accurately measuring the small amounts of Potassium Permanganate needed is difficult with a teaspoon.  Then we will add this to 6 jars of our fish water and watch the color reaction to determine how much PP we are going to add to the system. You will need the following: 6 clear glass jars with at least 1000ml capacity 2 clear glass jars with at least 500ml capacity Weight scales that will accurately measure grams 1 litre of distilled/de-mineralised water from the local shopping center 50 gram container of 1g/g (100%) potassium permanganate from the chemist (very expensive) 10 and 40 ml syringes also from the chemist or first aide supplies with accurate ml increments Glass stirring stick.  Don’t use a metal spoon or wood.  Plastic is ok Timer/stopwatch set to 15 minutes.  An alarm would be good. Protective clothing as previously mentioned Stock Solution (10,000mg/L) Weigh out 5 grams of the PP and add it to 500 ml of de-mineralised water in a clean jar, then stir well.  The water should turn pink in color and stay that way because there is no iron or manganese in the dematerialized water.  This makes up a strong stock solution of 10,000mg/L which we will further dilute. Testing Stock Solution (0.1mg/L) Because we are working with such small amounts of PP we want to be able to use easier to measure quantities, so we dilute our stock solution to make out testing stock solution.  Do do this we add 2ml of the stock solution to 200ml dematerialized water and stir well.   1 millilitre is difficult to measure, I suggest you use a child’s medicine syringe (5 or 10ml).  This makes a 0.1mg/L solution.  We will use this to test out PP demand on our fish tank water. The PP Demand Test We now fill our 6 x 1000ml jars (a little bigger would be good) with 1000ml of fish tank water.  So you remember which is which it helps to put a sticker or mark them with numbers 1 through to 6.  Add the following amount of the Testing Stock Solution to each of the jars using a 100ml syringe (with ml increments), set your alarm or timer to 15 minutes and stir well. Once solution is stirred and timer is going, you must observe the water color change.  Once the 15 minutes is completed, the jar which retains a pink color at the lowest concentration is the end point or indicator for the organic demand.  You then multiply the result by 2.5 to get your treatment rate per litre to add to your system. Example:  If our demand test indicated that Jar 2 (2mg/L) was the amount used by your organics, we then multiply that by 2.5 (2 x 2.5 = 5mg/L) to get our treatment of 5mg/L.  If we then calculate we have 1000 litres of water in our system, we add 5 grams (5mg x 1000 litres)  to our 1000 litre system. Next we will look at actually treating our system and things to watch out for. Regards Paul…

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