Very good idea !! Try this link for ref. as to the question about Ca.
http://srac.tamu.edu/tmppdfs/127565-464f...8bbc0e621462a54 Carbonates and bicarbonates are the most common and most important components of alkalinity. A
total alkalinity of 20 mg/L or more is necessary for good pond productivity. Total alkalinity is expressed
as milligrams per liter or parts per million calcium carbonate (mg/L or ppm CaCO3). In water with moderate to high alkalinity
(good buffering capacity) and similar hardness levels, pH is neutral or slightly basic (7.0 to 8.3) and does not fluctuate widely.
.gif)
