>That would be my opinion. A little calcium carbonate to provide >some pH stability and a little carbonate hardness for plants is the >only thing I can think of that really makes sense to add back to >RO/DI water. >Nathan H Isn't the calcium carbonate more for the plants, and the carbonate hardness more for the pH stability? The comments above say the opposite. Please help me understand this. I appreciate your help. TIA