I am currently dosing calcium and alk according to this recipe, but I'm not sure what dosing size I need. Right now I dose mixed tank, not bothering to do mag yet because I'm waiting on another gallon milk jug to empty out. I keep a chunk of montipora, two heads of hammer, two Astrea snails and a Conomurex luhanus in an 80 gal, and am planning to pick up birdsnest and maybe octospawn in the future. How much of all three(Ca, alk, Mg even though it'll be another week or two) should I dose?
There is lots to consider when dosing. No one will be able to tell you how much, they can only provide a starting point.
From there, you dosing amounts will change as your corals grow and the uptake of elements increases.