420 is fine - The perceived difference in Alk and Ca uptake is a very common misconception. Corals uptake Alk and Calcium at a consistent 1:1 ratio however there are variables that result in an apparent variance. For reference, every 1 mEq/L alkalinity (2.8 dKH) Alkalinity increase adds only 20ppm calcium. It takes a large ALk drop before you measure any noticable hange in Ca levels, so it "appears" that you are using more Alk then Ca.
A couple other variables can add to the confusion. Salt Mix - If your salt mix adds an imbalanced amount of either, it will appear as imbalanced usage in your testing. Mag - Low Mag or in some cases Strontium levels can impact Calcium/Alkalinity uptake.
pH changes with diurnal photosynthesis/respiration cycles and vary widely based on CO2 levels. It's not a good indicator of Alk or Ca unless you have known CO2 levels.
Originally Posted by CalmSeasQuest
Miz,
There's nothing like being a Reefer!
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