Orchiata Orchid Substrate makes a great substrate for orchids and will help them survive and thrive! Itâs a stable and pH adjusted medium with a Dolomite addition which supplies the essential nutrient calcium. Orchiata will not break down over time and become acidic. The size of this substrate is 3-6mm Precision, perfect for seedlings or young orchids. AFP 43-50%, WHC 52%