Emerald Harvest pH Down 1 Qt.In Store Location: C8 Emerald Harvest pH Down 32oz Emerald Harvest pH Down lets you fine tune the pH of the growing medium. This enables you to regulate the pH for optimal nutrient uptake and stable conditions for beneficial microbes living in the root zone. When the pH of the nutrient solution stays in the "sweet spot" (pH 5. 86. 3), sufficient essential nutrients remain available to the plant roots for heavy yields and bountiful harvests.