Flourish Potassium

  • Potassium supplement for the planted aquarium
  • Highly concentrated (50,000 mg/L)
  • Does not contain phosphate or nitrate making it ideal for use with Flourish Nitrogen and Flourish Phosphorus


Flourish Potassium™ contains 50,000 mg/L of potassium suitable for the natural planted aquarium. Potassium is one of several elements that are vitally important to maintaining a vigorous level of growth in a planted aquarium. Potassium can become depleted in a rapidly growing system or when the source water has a low mineral content. In these cases potassium could become the limiting factor to growth. Use Flourish Potassium™ to prevent potassium depletion (signs of which include yellowing in older leaves) and maintain the highest level of growth.

The most easily obtained sources of potassium are potassium nitrate and potassium phosphate. Both of these sources add to either nitrogen or phosphorus as well as potassium, making it virtually impossible to target a specific NPK ratio. Flourish Potassium™ is derived from potassium sulfate, allowing the user to adjust potassium levels without affecting nitrogen or phosphorus.


Use 1 capful (5 mL) for every 125 L (30 US gallons). This dose raises potassium by 2 mg/L. Repeat 2–3 times per week or as needed in response to signs of potassium deficiency in older leaves which include: chlorosis (yellowing), necrosis (death/browning), pinholes in leaves, and weak stems and roots.

Guaranteed Analysis

Soluble Potash (K2O) 5%

Derived from: Potassium sulfate

Elemental potassium is present at a concentration of 50,000 ppm (e.g 5%). Fertilizer laws require us to list potassium in terms of equivalence to a material that is not present (K2O) rather than the more scientifically sound method of simple elemental equivalence.


50 mL, 100 mL, 250 mL, 500 mL, 2 L, 4 L

To reach your desired level use:

caps or mL

Considerations: Repeat 2–3 times per week or as needed (in response to signs of potassium deficiency in older leaves which includes: chlorosis (yellowing), necrosis (death/browning), and weak stems and roots.

A: I nor anyone here has heard that rumor. From my experience, the level of potassium in a planted aquarium, with or without "Amano Shrimp" (most of the planted aquariums here contain them), can be maintained from 8ppm to 80ppm or even higher with no problems. If you are worried about over dosing potassium, which is hard to do because of the wide range of acceptable concentrations, our Flourish Potassium increases potassium concentration by 1ppm making it easy to slowly raise potassium levels.

Q: I have been using Flourite substrate and all the Seachem products and CO2 injection. I was wondering how do I know how much potassium to add, if I can add too much, or can I test for it. I use Equilibrium first then add potassium every other day. Any suggestions and is there a potassium test available?

A: Potassium is a major nutrient and I've seen a wide range of recommended values all with good success between 30 - 120 ppm. Our Equilibrium, if used at the recommended dose, will raise potassium to 50 ppm. The recommended dose of Flourish Potassium will increase potassium levels by 2 mg/L. As of now we do not manufacture a potassium test kit but there are some on the market that are available. The rate that you are dosing Flourish Potassium is definitely acceptable as this dosing regimen, along with using Equilibrium at water exchanges, should maintain potassium levels around 50 ppm depending on rate of consumption by your plants.

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0464 Flourish Potassium 50 mL
0465 Flourish Potassium 100 mL
0466 Flourish Potassium 250 mL
0463 Flourish Potassium 500 mL
0468 Flourish Potassium 2 L
0469 Flourish Potassium 4 L