Randy Holmes-Farley Recipe #2 calcium part (Part 1)
calcium
CaCl2·2H2O
Manufacturer data
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What one dose does
PARAMETER
1 ml / 100 L
Calcium
+0.185 ppm
To raise calcium by 20 ppm in 100 L: 108 ml.
How it’s used
250 g (about 1.25 cups) CaCl2·2H2O to 1 US gal -> ~18,500 ppm Ca. Half-strength partner to the unbaked-bicarbonate alkalinity part; dose ~2x the Recipe #1 volume.
Cautions
• Never dose the calcium part and the alkalinity part at the same spot/time or premix them; CaCO3 precipitates.
• Keep calcium increases <=50 ppm/day for large corrections (BRS guidance).
• Two-part dosing adds NaCl as a by-product (CaCl2 + Na2CO3 -> CaCO3 + 2 NaCl); monitor salinity and do periodic water changes.
• Ice-melt products vary in purity and hydration; unknown brands are untested for heavy metals.
• Hydration state changes Ca per gram: anhydrous 36.1% Ca, dihydrate 27.3%, hexahydrate 18.3%.
Sources
250 g made up to 1 US gal total.
reefkeeping.com/issues/2006-02/rhf/index.php