[dumbdumb12345]

A few weeks ago, I poured a few grams (can't remember exact amount) of potassium permaganate crystals into some warm-hot water on a friend's advice in order to help my crushed toenail heal faster. I didn't stir...the crystals mostly sank to the bottom and the water took on a purplish color. After bathing my foot for a few minutes, I decided to nope out of it. There was no visible staining. I let it dry for a little bit then washed my foot in the shower.

What's the likelihood that there still was residue remaining after washing my foot; after these weeks, is there still residue possibly remaining? Say I visit a river and go for a swim - would there be adverse effects on the organisms there?

Sorry if this is a really stupid question. I regretted taking my friend's advice the moment I searched up some of the downsides of using potassium permaganate.

[chenbeier]

There is no problem. Permanganate will be convert to Manganesedioxide MnO₂. This is brown, probaly seen on your feet or the sink of the bathtube.

[pcm81]

In low concentrations potassium permangenate is used as sanitizer and people even drink water sanitized by KMnO4. If the foot is sill brown and the color is bothering you, you can use dilute ascorbic acid to wash it off. I even used dilute Oxalic acid on my own hands with no adverse effects.