Magnesium

Water Parameter
Magnesium
Unit(s):	ppm
Target:	1,250 - 1,350 ppm
Danger:	< 1,000 ppm > 1,500 ppm
Tendancy:	Decrease
Increased:	Additive Water changes
Decreased:	Precipitation
Testing:	Monthly
Maintenence:	Magnesium chloride Magnesium sulphate

Introduction

Magnesium is the third most abundant element in seawater, with only chloride and sodium have higher concentrations. Normal seawater has a concentration of magnesium of around 1320 mg/L.

It is important to maintain magnesium at or around natural levels (1320 mg/L) to avoid problems with alkalinity and calcium concentrations. This is due to the poisoning nature of the magnesium to the calcium carbonate crystal structure, making the crystal harder to form when it is at the appropriate concentration.

Chemicals that can be used as an additive for magnesium:

• magnesium sulphate, anhydrate or heptahydrate
• magnesium chloride, anhydrate or hexahydrate

Resources

• Magnesium in Reef Aquaria by Randy Holmes-Farley - Advanced Aquarist's Online Magazine
• Magnesium and Strontium in Limewater by Randy Holmes-Farley - Advanced Aquarist's Online Magazine
• Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping Magazine
• Magnesium Additive by Dallas Warren - OZ REEF