Potassium sulphate

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K2SO4Potassium sulphate (Potassium sulfate (USA spelling)) : Provides Potassium (K) for feeding aquatic plants.

Quite often in a planted aquarium the plants absorb so much potassium that it becomes a shortage and limits the growth of the plants. So aquarists often add it manually.

To make a typical stock solution add 55g of dry K2SO4 powder to 500ml of RO or distilled water and then add 40ml of this per 100L of tank. This will give you a value of 20ppm (20 mg/l). You would dose 3 times a week when using the EI method.

  • Adding potassium sulphate at the rate of 0.011g per litre to a tank will increase the potassium (K) level by 5ppm.
  • Example commercial product is 'Sulphate of Potash', a common gardening fertiliser. Typically says it contains K2O (Potassium oxide). But it's really Potassium sulphate. See this example product web site.
  • See PMDD for more details.


  • Garden shops - Look for 'Sulphate of Potash' and check that the ingredients only say it contains K2O.