LPS calcium and alkalinity

[Myka]

For every 20 ppm of calcium used, 2.8 dKH of alkalinity will be used up.

For an LPS system I find it can often be maintained by just using waterchanges with slightly higher values than you're aiming for. For example add a bit of cal/alk/mg as needed to achieve cal 440, 11 dKH, 1450 mg in the freshly mixed saltwater. Use this slightly saturated saltwater for 10-20% weekly changes and you may not need to dose the tank directly.