Is Potassium Permanganate. (KMnO4) a useful Med or a deadly killer? Or what I do with PP and Why.
By teddy,J

Make no mistake. PP is a deadly killer. Just like many other chemicals/meds that folks add to their aquarium water, used wrongly it will be bad for your fish. Like all medications it must be administered EXACTLY as prescribed otherwise damage or death will be the only result you will get from its use. PP will dissolve/oxidize all living matter be it animal or vegetable when used in strong enough solution. PP is DANGEROUS STUFF. and used unwisely/carelessly can and will dissolve your fishes gills and turn your plants into a slimy mess.

In simple terms ‘cos I’m a simple bloke and this is how I see it. When PP is added to water it makes the water go a purple colour. As the PP works and destroys matter it dies and looses the purple coloration and slowly becomes cloudy brownish. Once the purple colour has gone the PP is no longer working. With all PP treatments the idea is to keep the water just the right shade of purple for the required time. I always have two loaded syringes handy, one with PP base mix in it, so that I can add extra PP if the purple colour fades before the treatment time is up, and the other with the Antidote (more later) in it.

That warning being made I will now tell you what I use PP for and how I use it.

The base mix that I use is:- 1 gram PP (1/8th tsp.) crystals added to 400 mls water.

There are antidotes to PP. One antidote is Sodium Thiosulphate and another is Hydrogen Peroxide (HP). I use HP. which comes in two different strengths here in Australia 3% and 6%. I prefer to use the 6% but that is just a matter of personal choice. These compounds stop the oxidization process almost immediately, and in my opinion PP should never be used around fish without an antidote being ready in a syringe in case of an emergency..

The most common usage I have for PP is to make fairly sure my top up water is clean and contains virtually no Bio Load. (Bacteria and Parasites) When I suspect the quality of the water supply which varies quite considerably in my area. I use it to kill most of the living matter in the tap water when preparing it for my fish I start by adding 2 mls base mix per gal and leave it for 1 hr. (remember the water has to stay purple and more PP may be required if the water has a heavy Bio Load).

I then. add 6 mls of HP to a 50 gal tank More HP may be required depending upon how much PP has been used. There will be a temporary rise in pH readings but that has never bothered my fish. My top up water is always allowed to stand for 24 hrs before I use it.

Another time I will use PP is if fish are scratching and rubbing themselves against objects in the tank excessively. I do a complete check of the water parameters particularly Ammonium and NitrItes and if all readings are as they should be I assume that something is ‘getting at them externally’ There are various methods of dealing with this problem some of which include using deadly drugs like Dylox (Fluke Tabs) and Formalin. These meds are invisible in solution and can not be controlled in the water in case of problems. They also require several days to kill most ecto parasites (if they work (have any effect) at all) I believe all the commercially available (LPS/LFS) treatments are too unreliable, expensive and stressful for my Discus. I refuse to use those meds ever again (I've lost too many fish to them). I use the base PP mix at 4 mls to the gal US for 4 hrs. (remember it has to be kept purple so you may have to add extra PP) MAXIMUM DOSE I would ever use is 6 mls per Gal US. (1.5 mls per ltr.) Go higher than this for any length of time and you could well be damaging your fishes gills and eyes. Beware!! overdosing is not smart.

My fish are kept under PERMANENT observation during the time that PP is in their water, and if there are any signs of the fish being in distress I use the antidote HP which I have available in a syringe before I start the treatment. Usually 1 treatment is sufficient to remove all ecto parasites and the fish return to normal behaviour. (cured in 4 hrs) In the case of parasites which may have left spores/eggs/cysts in the water re treatment will can be performed when you see scratching again.

Sometimes for no apparent reason my fish decide to go black and develop white slimy patches on their sides. You can even see the white marks on their sides where they rest their Pectoral fins sometimes. (This has happened to just 1 fish in a tank or several all at the same time or one after another over a couple of days)

I always check the water parameters which are usually OK, the fish are not noticeably off their food and eat when I feed them, but there is obviously something wrong ‘cos they are black and hanging about listlessly with their fins down (I guess (assume) there’s a pathogen in the tank). This is another time when I reach for the PP and dose at 4 mls per 1 gal US (1 ml per ltr) for 4 hrs. (I never forget the HP). Then, after the PP treatment is over, I turn up the temperature to 95F and add sea (cooking) salt at 2 tblsp per 10 gals. The lost salt is replaced daily as I do water changes. I expect to see improvement in the fish in around 3-5 days and a full cure within 10 days.

My reasoning for that treatment is to kill the external problems (pathogens etc) with the PP first. This I believe will give the fish the respite/relief from pressure they need and then their own metabolism should take over and fight any internal bugs if the temp is raised a bit to help ‘em.

Another warning.

Many years ago I killed every fish and plant I had by being lazy and not measuring the dose of PP that I put into a 6’x2’x2’ planted community tank. The whole lot turned into a slimy mess. I can’t emphasise enough the dangers of misusing any med but particularly don’t mess or guess with PP.

If you are not capable of measuring small quantities accurately, then don’t use PP. Syringes come in several sizes and only cost a few cents and are available at Pharmacies. You don’t want to buy the ones with needles

There are experienced aquarists who will not use PP ‘cos they believe it is too dangerous or for whatever reason. That is their right and they are probably doing the right thing by themselves and their fish. The treatment/health of Aquarium fish is solely dependent on the owner and I have found that PP works well for me and my Discus.

Potassium Permanganate (KMnO4) is cheap and easy to use and does the job that is required of it quickly and efficiently.

Please always remember it is deadly and dangerous. It MUST be measured accurately and IMO must NEVER be used without having the antidote ready.

I regard PP as being one of the most useful and reliable meds available to Aquarists.

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