I can't eplain it exactly. I mix some of the crystal powder with water in a liter bottle. I pull the sponges from the filter and put them in a bucket. The i pour some of the purple PP water into the tank . . . a dollop at a time until the water is medium purple. Watch the fish, leave the PP in the tank for 4 hours, then add hydrogen peroxide one capful at a time until the water turns clear. Then I do a partial water change. Finally I put the rinsed sponges back in the tank.