Magnesium Chloride 1 litre (840g)


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Magnesium Chloride – 1 Litre

Maintaining proper magnesium levels prevent excess calcium carbonate precipitation by achieving the essential balance of calcium and alkalinity in your tank. Magnesium Chloride is crystalline hexahydrate and dissolves crystal clear and makes them easier to measure than larger flakes.

Magnesium Chloride may be used as a standalone magnesium supplement or mixed with Magnesium Sulphate as part of the popular 2 Part Calcium and Alkalinity solution.  Bromide, Ammonia and Phosphate Free.

Using Magnesium Chloride

  • Test current magnesium level
  • Use a online Reef Calculator or
  • Add 1 teaspoon (4.4 g) per 10 gallons to raise magnesium by approximately 14 ppm
  • Dissolve appropriate amount in RO/DI water and let sit before use
  • Slowly add solution to a high-flow area, ideally into a sump
  • Re-test and repeat dose until desired level is reached

Magnesium Chloride can be used in conjunction with Magnesium Sulphate to more closely match the natural ration of seawater.  Add 5 level cups of Magnesium Chloride and 3 level cups of Magnesium Sulphate to a one gallon jug and mix with RO/DI or distilled water. Let sit before use.


Do not add Magnesium Chloride directly to your aquarium water. Always test magnesium levels prior to use. Magnesium concentration found in natural seawater is between 1,250-1,350 ppm. Due to the sensitivity of marine organisms, it is not advisable to raise magnesium by more than 100 ppm per 24 hours.

Due to the variation of granular size, conversion between volume and weight of powdered products is approximate. As a precaution, dose less than the calculated amount and measure the effect before adding the total amount.


This product becomes hot when mixed with water; use rubber gloves. Avoid contact with eyes, skin, and clothing. Wash hands after handling.

Additional information

Weight 4 kg