Potassium deficiency in aquatic plants

Potassium deficiency in Hygrophila corymbosa

Water values

  • KH: 3 °dH
  • Conductance: 280 µs/cm
  • Iron: ~ 0.05 - 0.1 mg/l
  • Nitrate: ~ 10 mg/l
  • Phosphate: ~ 0.1 mg/l

Water change approx. 50 % per week with reverse osmosis water mixed with approx. 10 % tap water. In addition, the water is hardened with one of the commercially available disc salts.

Despite daily fertilisation with KramerDrak for about 4 weeks, supplemented with Eudrakon P, the potassium deficiency has unfortunately increased considerably, as can be seen very clearly in the photo.

* Photo used with the kind permission of M. Manser (infinity)

The punctiform necroses on Hygrophila corymbosa, which always appear first on the older leaves, ultimately spread over the entire plant if the potassium deficiency persists. The commonly used aquatic plant species of the genus Hygrophila are among the most sensitive to a sub-optimal potassium supply and can therefore be successfully used as so-called indicator plants. They show symptoms long before plants of other species do. The only remedy is to provide a sufficient supply of potassium-containing preparations, regardless of whether the source is fertiliser, water conditioner or hardening or mineralising salts.


There are probably several causes in this case.

Even if the tap water is very rich in potassium, the potassium concentration is reduced to 10 % of the original concentration by blending with UO water. Unfortunately, most commercially available salts skimp on potassium salts as they are not among the cheapest components. A water conditioner containing potassium was also not used.
As a result, the supply of the nutrient potassium remained far below the requirements of the plant community in this aquarium, which was shown by the severe necrosis of this H. corymbosa.

When designing and producing all DRAK aquarium preparations, we therefore always ensure that there is an adequate supply of potassium, so that such massive deficiency symptoms very rarely occur when using our fertilisers, hardening salts and water conditioners.