===== potassium (K) =====

In the context of aquariums, potassium is an essential nutrient for aquatic plants. It is one of the macronutrients required for plant health, alongside nitrogen and phosphorus. 

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==== Signs of Potassium Deficiency in Aquariums ====

  * **Yellowing of Leaves:** Older leaves often start yellowing, especially around the edges, which is known as chlorosis.
  * **Pinholes in Leaves:** Potassium-deficient plants can develop small holes in their leaves, which may eventually spread.
  * **Poor Growth:** A lack of potassium results in stunted plant growth and weak, fragile stems.