KH
buffering capacity, temporary or carbonate hardness, measured in degrees (K is from the German word karbonate). KH makes up a component of GH, q.v., so boiling will also reduce GH slightly. One degree KH is equal to 17.9 mg/l CaCO3. The degree symbol may be replaced with a d, e.g. 2 dKH)
Dictionary of ichthyology.
2009.