Water Hardness
GH is the unit used to tell us the General hardness of the water. Or how much Calcium and/or Magnesium are dissolved in the water.
Only Calcium and Magnesium are measured and not the overall amount of dissolved solids. The GH level isn't really of importance unless you want to breed your fish or unless it is extremely high.
Excessive amounts of Calcium in the water will affect the fish's fertility and it will also make the outer membrane of the eggs tougher so that fewer eggs will be fertile and those that are fertile may fail to hatch. There are not very many fish that prefer really hard water other than some African Cichlids (from Lake Tanganyika) and some Livebearers.
Lowering the GH.
- Diluting the water with R/O, DI, or even collected rainwater.
- Using an ion exchange resin. But this method has its drawbacks, because if the resin is recharged using water with salt added (and most are) then although the Calcium and Magnesium are removed making the water softer, they are replaced with something else so the overall dissolved solids remain the same.
Raising the GH.
- Add some calcareous rockwork or gravel to the aquaria.
- Use a proprietary product such the salts intended for African Cichlids.
