A single reagent test kit with a small glass graduated cylinder. Place single drops of reagent in the sample and count the number of drops for the sample to turn from blue to yellow. The color change is dramatic and unambiguous.
The total number of drops equals the number of German hardness degrees (multiply by 17.9 to get ppm). As a result the resolution of the kit is only 1 degree of hardness. That\'s probably not good enough for the rocket scientists but it\'s good enough to get a general result for CO2 calculations.
The kit is relatively inexpesive at €8 ($11) locally, however I operate in the very soft water regime rarely exceeding 5 degrees using RO water mixtures so one kit serves me for a while. Others having hard water may disagree.
Like every test kit it\'s always a good idea to calibrate against known samples after opening the box.
The kit can be used for both salt and fresh water. As with other Sera kits the instruction sheet is written in 20 languages resulting in very small font text, taxing the eyeball.
Ease of use
Small font size on instruction chart, limited accuracy