Potassium Permanganate KMnO4 Treatment Or PP In The Aquarium


Lifetime Charter Member
Lifetime Member
Jun 21, 2009
Surprise, AZ

I have had a couple of questions regarding Potassium permanganate (KMnO4) treatment so this is the method I use. :cool:

Remember to use care in handling KMnO4 and never ever mix it with Formalin. :eek:

The Potassium permanganate (KMnO4) treatment is explained at http://edis.ifas.ufl.edu/fa027. I have found the Potassium permanganate treatments at these levels safe for my critters down to shrimp; it will harm populations of smaller invertebrates, but then that is the idea in this case.

I recommend that you experiment first with a couple of your critters prior to treatment in the main tank. If you have never done this before be extra vigilant, err on the low side in concentrations. Should you notice any adverse reaction or just find yourself pooping uncontrollably, add whatever de-chlorinator you use at the proscribed rate.

One of the reasons I like the Potassium permanganate method is that it is also a good indicator of water quality. Take an 80-USgallon tank.
We need 2mg/l of PP so:
Grams of PP=80-gallon*0.0038*2mg/l=0.6-g PP
(if you have a scale accurate enough and are using lab grade Potassium permanganate, feel free to measure out 0.61 or 0.608 g of PP).

Dissolve the PP into a liter of aquarium water, and then pour the solution along the length into the aquarium. Note the time or set an alarm for four hours.
The aquarium water should turn a pleasant pink or even light purple (were it not for the profanity laced replies from the Plant Guru Team, I would tell you the approximate ORP values the different colors tend to represent).
Light purple means your water quality is excellent and you can even use a little less PP the next time. Pink is also an indicator of good water quality and that the dosing is correct. Yellowish tint through mud brown indicates poor water quality and the quicker and darker it got the worse the water quality.
If your aquarium got into the yellow to dark browns in less than four hours, add another 2mg/l dose that is another 0.6 grams of PP. Continue the process until you make it four hours in the pink. The color may, in fact should fade, to pretty much invisible, if not add some de-chlorinator to the water.
Most discover that excellent water quality tends to preclude many of the critter problems.

Back in the day as the Earth cooled, before the knowledge of water changes this is the way we removed the organics from the water. ;) Many pond keepers even unto this day use this process since major water changes may be prohibitive or even impossible. :gw



Guru Class Expert
May 24, 2009
Montreal, Canada
Good stuff Biollante!

Ah... removing organics without water changes. :gw

I use 30% H2O2 for that since I have some. I've noticed a lot more bubbles if there's a lot of detritus mulm in the tank. Don't you just hate it when you wake up and find a detritus mulm swimming in your tank. He may be a fellow Canadian but I would still rather not see him in there :p

I never thought of using PP though.

Thanks for the info.