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 red to green. The color change is much less dramatic than in Sera\'s kH kit and therefore it can sometimes be ambiguous.
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. I don\'t use this kit as much anymore because I have a Hana Pocket ph/TDS/temp meter. I use RO water and regulate the tank to kH and TDS and therefore have no further need of GH measurements.
The kit is relatively inexpesive at €8 ($11) locally, however I operate in the very soft water regime using RO water mixtures so one kit would serve 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 is a fresh water only. As with other Sera kits the instruction sheet is written in 20 languages resulting in very small font text, straining the eyeball.
GH is another one of those fundamental measurements of which a kit should be in everyone\'s arsenal. This kit does a creditable job.