Magnesium Sulphate Heptahydrate - Technical grade


SKU: RD10235

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Technical Grade 

Magnesium sulphate heptahydrate is a soluble crystalline compound with many applications. It is a type of salt and mineral which is found in the geological environment. This can be obtained from the ore, epsomite, a white solid substance found on the surface of the earth also it is in oceans and springs.


PLEASE NOTE: This product is not for human or animal consumption.


Uses for Magnesium sulphate 

Magnesium sulphate is used to maintain the magnesium concentration in marine aquariums which contain large amounts of stony corals as it is slowly depleted in their calcification process. See below - Using Magnesium Sulphate in marine aquariums.

It is also used in the manufacture of matches and in the cotton and silk dyeing industry; increasing the bleaching action of chlorinated lime; manufacture of mother-of-pearl and frosted papers; fire-proofing fabrics; dyeing and printing calicos;

Magnesium sulphate is used in fertilizers for agriculture and gardening. Known for accurate composition, this fertilizer increases the productivity of crop plants and does not affect the fertility of the soil.

Using Magnesium Sulphate in marine aquariums

In an aquarium with low magnesium levels, calcium and alkalinity concentrations are difficult to control because there is a lack of magnesium present to stabilise these ions in the saltwater and prevent their natural precipitation into calcium carbonate.

You should aim to maintain Magnesium levels at around 1300 to 1350ppm using a good quality reliable test kit. 50g (10 teaspoons) will raise Magnesium levels by approximately 50ppm in 100 litres of salt water.

Simply dissolve the required amount into a few litres of Reverse Osmosis Water, mix well and slowly add to your tank in an area of high flow, preferably over a period of an hour or so using a drip line or peristaltic pump. Alternatively add to your evaporation top up water and top up as normal.

It is not recommended to increase Magnesium levels by more than 60ppm per day.


Properties of Magnesium Sulphate:

  • Synonyms: Magnesium sulfate heptahydrate;
  • Appearance: off-white crystals
  • Mg SO4.7H2O: > 98%
  • Magnesium sulphate (MgSO4): 49.1%
  • Water: 50.9%
  • Sodium: 40 mg/kg
  • Potassium: 230 mg/kg
  • Calcium: 60 mg/kg
  • Chloride: 80 mg/kg
  • CAS No: 10034-99-8
  • EINECS No: 231-298-2
  • Mol weight: 246.48
  • Melting point: 1124 C
  • Bulk density: 850 g/dm3 approx
  • Density: 2.7 g/cm3
  • Solubility: soluble in water 246 g/l in water at 20C
  • pH: 5.0 - 8.0 at 50 g/L

Health & Safety:

Not a hazardous substance or mixture according to Regulation (EC) No. 1272/2008. This substance is not classified as dangerous according to Directive 67/548/EEC.


Click here for MSDS

Click here for Technical sheet