DIY magnesium blend (MgCl2·6H2O + MgSO4·7H2O)
magnesium
MgCl2·6H2O + MgSO4·7H2O
Manufacturer data
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What one dose does
PARAMETER
1 ml / 100 L
Magnesium
+0.47 ppm
To raise magnesium by 50 ppm in 100 L: 106 ml.
How it’s used
Pharma/USP magnesium chloride hexahydrate flake + unscented USP Epsom salt (or BRS Pharma versions).
Cautions
• Part 3 cannot be premixed with the calcium or alkalinity parts (sulfate + Ca -> CaSO4; Mg + carbonate -> precipitate). Some CaSO4 haze in the jug is expected; shake before dosing.
• Ratio choice: sulfate-rich blends (RHF Part 3A, 5:3 by cups = ~1.4:1 by weight; BRS 2-part version ~2.8:1 by weight) are meant to be used WITH a CaCl2-based two-part, whose chloride load needs extra sulfate; a stand-alone Mg supplement for corrections is better at ~10:1 MgCl2:MgSO4 by weight (RHF, relayed; BRS general mix 1285 g:124 g).
• Raise Mg no more than ~100 ppm/day; wait 5 days off-dosing before setting a maintenance dose (BRS).
• Cup measures are approximate; weigh where possible.
pH effect: neutral.
Sources
Pharma/USP magnesium chloride hexahydrate flake + unscented USP Epsom salt (or BRS Pharma versions).
reefkeeping.com/issues/2006-02/rhf/index.php
bulkreefsupply.com/instructions/article/brs-pharma-magnesium-dosing-instructions
bulkreefsupply.com/brs-bulk-magnesium-sulfate-aquarium-supplement.html
reefcentral.com/forums/archive/index.php/t-954123.html