Plantex CSM+B may contain some calcium or magnesium salts that could slightly increase your GH
, but nothing significant. To increase your GH
you need to add something like calcium sulfate, calcium chloride, or magnesium sulfate. You can also buy pre-mixed GH
buffers like Seachem's Equilibrium or Kent's R/O Right. These products are designed add some general hardness to reverse osmosis water and would work well for increasing GH
in any type of water.