Unlike kH which is the specific measurement of calcium, gH (general hardness) is the measure of all the salts and ions in your water, including, but not restricted to, the two most important to our Koi: magnesium and calcium.

gH is expressed in degrees, with one degree being 17.9 mg/litre. They then give you a table to show if you water is hard or soft with numbers like: 0-4 degrees = soft water, and 18-30 degrees = hard water and a whole lot of complicated numbers inbetween. We say – so what does that really mean? and even more important, what does it all mean for our Koi?