Dissolved Carbonate Hardness (dKH)

Last updated: November 18, 2021

What Does Dissolved Carbonate Hardness (dKH) Mean?

The carbonate hardness of water, also known as carbonate alkalinity, refers to how the alkalinity of water is measured. It is almost always expressed as parts per million (ppm or mg/L), or in KH (dKH) degrees.

For optimal health of the species within, the dissolved carbonate hardness in an aquatic system is usually less than 4dKH.

An aquaponic system with a dissolved carbonate hardness does not have a much-buffering capacity and will often experience rapid swings in the water’s pH that occur frequently. In such a situation, fish often start to die.


Maximum Yield Explains Dissolved Carbonate Hardness (dKH)

To determine if the water’s pH is at 4dKH, a carbonate hardness water test should be performed. A carbonate hardness water test, called a KH, determines the water’s alkalinity and will reveal its buffering ability. If the carbonate hardness test reveals a 4dKH level then the water is considered to be in a state of dissolved carbonate hardness and the pH level must be stabilized for the well-being of the aquatic life.

With an aquatic dissolved carbonate hardness system of less than 4dKH, the water’s pH should be managed and measured on a daily basis. Needed adjustments will more than likely be required to alter the dissolved carbonate hardness system. A lack of carbonates in the system is not only deadly for fish but also promotes unwanted bacterial growth in the water. Managing the water’s pH is critical in aquaponics and hydroponic gardening. The ideal target pH for both systems is usually pH of 6.8 to 7.


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