Potassium is one of the macroelements which is quickly and effectively absorbed within a few hours and temporarily stored by plants in freshwater. In growing plants the demand for potassium is higher than other elements. As a result, potassium concentrations can drop to a minimum range, causing plant growth to stagnate, even if the aquarium water is fertilised regularly (e.g. weekly). Potassium levels in mains water are usually too low compared to those in natural biotopes, particularly in relation to calcium and magnesium concentrations.
How often should you test?
Firstly we recommend you measure the potassium content of your aquarium water daily. This way the plants’ needs can be determined and the fertiliser can be dosed appropriately. After that you can continue the routine measurements less frequently.
What is the ideal content?
For good plant growth the value needs to be approximately 5 - 10 mg/l, for aquariums with high power lighting (from about 1 W/l illuminance) between 10 and 30 mg/l. Higher potassium levels in the aquarium will lead to the growth of green thread algae.
Action, when too much or not enough
Potassium content too high (> 20 mg/l): Repeat measurement after 24 hours. If value is still too high, carry out an adequate water change.
How is the test carried out?
This short video shows you how easy it is to carry out the JBL K Kaliumtest .