(4 customer reviews)
Potassium Sulfate Pure 99.5%

Weight 90g 250g 500g

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Potassium Sulfate, Pure

Other name

Potassium Sulphate

Sulphate of potash

CAS Number 7778-80-5

EC Number  231-915-5

E number  E515

Chemical formula K2SO4

Solubility in water 111g/l (20 °C)


50g K2SO4 + 500ml water, 1ml solution per 100 l of tank water yields a concentration of 0.45 K ppm

25g K2SO4 + 500ml water, 1ml solution per 100 l of tank water yields a concentration of 0.22 K ppm

K2SO4 should last for about 250 days (for a 100L aquarium), it’s worth remembering that KNO3 and KH2PO4 also contain potassium.

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

Potassium (K)

Potassium is a macroelement, it makes about 1% of a dry plant. This element activates over 50 enzymes, takes part in osmoregulation and in ion balance maintenance. Potassium is a mobile element, therefore symptoms of its deficiency occur in older leaves first. Plants absorb potassium in the form of ions K+. The most commonly used source of potassium is potassium sulphate (K2SO4) and potassium chloride (KCl). The recommended level of potassium is from 5 to 20 ppm a week. In planted aquariums, in which this element is not provided, there is a high likelihood of its deficiency. Tap water doesn’t have enough of this element to meet the plants’ needs. When it’s necessary to dose KNO3 to maintain a good level of nitrates, further dosing of potassium would not be necessary.

Potassium deficiency

In planted tanks potassium deficiency is quite common. In case of moderate deficiency usually the only symptom is impeded growth of the plants (in more severe deficiencies the growth is completely blocked). Chlorosis of older leaves’ tips and edges, often leading to their necrosis, in more severe potassium deprivation spreads to the leaves’ blades (the main veins remain live however). In other cases, yellow, brown or white spots, also leading to necrosis, appear on plants’ leaves. Potassium deficiency also manifests itself in chlorosis between the veins throughout the whole leaf blade. Some sources also suggest symptoms such as growing points withering, fragile sprouts, poor development of root system and leaf fall (in more severe cases).

Potassium excess

The most often mentioned effect of excessive potassium is magnesium or calcium deficiencies. Other sources also indicate manganese, nitrate, zinc and iron deficiencies. Some sources suggest that excess of potassium is harmless. Some aquarists providing high doses of potassium (20 ppm a week or more) noticed young leaves deformations and growing points withering. Such problems were particularly evident in Ammania gracilis plants.

Additional information

Weight N/A
Product Weight

90g, 250g, 500g

4 reviews for K2SO4

  1. thomas


  2. Robin


  3. Anna

    Very good quality, thanks for extras.

  4. khastieviirza

    Very nice fertilizer.

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