i hadnt thought about that before, but water changes actually would take some of the still-present K out of the water. my current calculations have me adding 20ppm of K per week @ ~7ppm 3x each week. If I am doing 3 30% water changes a week (for my Discus), i should be adding more, correct? my water change schedule is on Tuesdays, Thursdays, and one of Saturday/Sunday. Do you think the plants consume the K fast enough that just adding 1/3 after each water change is fine? Or should I make up for the additional amount lost?
I mix my KNO3 and K2SO4 by adding 2T to 200ml water in individual bottles so I can add seperate. Then from this mixture I would, when I don't have any measurable KNO3, add 20mls of KNO3 to get 5ppm of nitrates. Then I would add double the amount of the K2SO4 mixture.