Karen,

Is your pool plaster or does it have exposed grout anywhere (on a tile line, for example) or is it a vinyl lined or fiberglass pool? If it's a plaster or exposed grout pool, then you definitely have to have calcium in it, otherwise your pool water will slowly dissolve your plaster and grout. If it's vinyl or fiberglass, then you don't need the calcium.

By the way, if your pool is plaster or has exposed grout, then any dissolving of the plaster or grout would result in your pH and alkalinity increasing over time just as if you were adding soda ash (calcium carbonate) to your pool. Since you have high pH and alkalinity, perhaps this is what was happening with you (which wouldn't be good -- if your pool surface is plaster, does it look pitted or has it been getting rougher over time?).

Richard