Magnesium Sulfate Pure BP

Food Grade MgSO4x7H2O

Weight 90g 250g 500g 1kg

SKU: N/A Category:


Magnesium Sulfate, Pure, Food, Pharma Grade

Other names

Epsom salt, Magnesium Sulphate,  Magnesium Sulfate Heptahydrate, English salt, Bitter salts, Bath salts

CAS Number 10034-99-8

EC Number  231-298-2

E number  E518

Chemical formula MgSO4x7H2O

Solubility in water 710g/l (20 °C)


250g MgSO4x7H2O + 500ml water, 1ml solution per 100 l of tank water yields a concentration of 0.5 ppm Mg

100g MgSO4x7H2O + 500ml water, 1ml solution per 100 l of tank water yields a concentration of 0.2 ppm Mg

50g MgSO4x7H2O + 500ml water, 1ml solution per 100 l of tank water yields a concentration of  0.1 ppm Mg

The best practice is to add the recommended week’s worth dose of magnesium at once during water change.

The recommended dose is 3-10ppm of magnesium.

In highly concentrated solutions, magnesium may react with phosphorus creating insoluble compounds.

Store in dark place, in room temperature.

In order to measure the required amount you can either use a scale, a measuring jug (with milliliters), a teaspoon or a tablespoon. If you want to use spoons, it is important that you use the same spoon for all of your mixtures. The size of the spoon is not that important – it is the maintenance of the proportions of all of the ingredients that matters.

Just to give a rough guide: 1 teaspoon = approximately 5g, 1 tablespoon = approximately 15g.

What also needs to be remembered is that every chemical compound has different maximum solubility in water and that the values given above are accurate for distilled water. The maximum solubility in RO water will be slightly lower; solubility in boiled water will be even lower (if you want to use boiled water, we recommend you to boil it for 3min and than let it drop to room temperature).

It is worth mentioning that saturation of a solution of one salt will decrease the solubility of another salt added to the same solution.


Good To Know

Magnesium (Mg)

Magnesium is a macroelement, it makes about 0.2% of a dry plant. Magnesium is a component of chlorophyll; it also activates many enzymes. Some sources classify magnesium as a mobile element (can transfer from one part of the plant to another), therefore symptoms of its deficiency occur in older leaves first. Plants absorb magnesium in the form of ions Mg(2+). In case of this element, its level is not as important as its proportion to calcium. The most commonly used source of magnesium is magnesium sulfate heptahydrate MgSO4x7H2O.

Magnesium deficiency

Interveinal chlorosis (sometimes in the form of spots) first occurs on tips and the edges of the leaves, then it spreads to the center of the blade; the leaves’ veins tend to remain green. With time the deficiency symptoms may also spread to younger leaves. Other sources suggest that deficiency symptoms most likely occur in upper and middle leaves. The areas affected by chlorosis may also change the colour from yellow to brown (or even lilac and red). In the case of more severe deficiencies, necrosis and leaves withering may occur. Sometimes leaves may start to fall event before other symptoms (e.g., change of colour) are noticeable. Some sources suggest that young leaves may become bent and their size may decrease.

Magnesium excess

Generally, the excess of magnesium is harmless. Some sources indicate that the excess of magnesium may lead to deficiencies of calcium and potassium.

Additional information

Weight N/A
Product Weight

90g, 250g, 500g, 1kg


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