Hi Shango, I didn't want to spend a lot of time testing my NPK. And although I do 10% - 20% water changes weekly, I didn't want to "have" to do it every week. So I went with the PPS-Pro method and try to keep it as simple as possible. Hope this helps! http://www.aquaticplantcentral.com/forumapc/fertilizing/ Roy _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member