Potassium Permanganate- Or, “PPâ€, can be found online, or you local phamarcy
You add just a few grains of this to a container or sink and then add the water. It takes it a little while to dissolve, but no big deal. Your goal is to get a good dark pink tint to the water. Once you get it a good dark pink ( but not light pink, not dark purple), add the plants and give them a bath for a good 15 to 20 minutes or so. After that, drain and add fresh water. Stir in some dechlorinator or hydrogen peroxide, both of which will neutralize PP. You can go heavy on the dechlorinator, but don’t go overboard on the hydrogen peroxide. Rinse plants again, quickly, and they should be ready.
HTH