Cal mag? How about that pH Down? Citric acid works great, is cheap, comes in powdered form for stable storage before prep. I run nothing but tap water and use it as my pH Up. Many experienced hydro growers use straight tap water, hardness permitting, and simply adjust the pH. Besides your Micro should have all the cal, mag, copper, iron etc it needs. Check the label. GH is awfully expensive stuff.
Oh yeah I pointed out the bit about the pH Down because all acids or buffers have a shelf life, especially once opened. Product stability is a question. A big bottle of pH Down could last in volume far longer than it is stable. Powdered citric acid stays stable if dry and can be mixed precisely in small batches.
