I wonder why when folks use this method; most seem to have sickness in their tanks. Most discus diseases begin with dirty/water related issues. When the word "pristine" in most cases is used for discus. I would not take this approach; I cannot get antibiotics in my country and can't risk not being more diligent with maintenance and WC's. That method has been around since the aquarium hobby started. And most find it does not work with discus. Sounds like a good way to get "old tank syndrome".