What is pH and Hardness? pH refers to the acidity or alkalinity of water. Different fish have learnt to adapt to different pH levels, thus, it’s important to know the requirements of your fish. Although many fish can adapt to a range of pH levels, fluctuations outside this range may well prove fatal.
It is important therefore to remember that readings should be taken regularly from specimen water samples and adjusted as appropriate. Proprietary water treatments can be bought which will alter (buffer) pH levels.
There is a direct relation between pH levels and the toxicity of ammonia. When pH levels are low, ammonia is less toxic.
The origin of your water determines its hardness. Water originating from rain absorbed through the likes of chalk, limestone and clay is hard. That absorbed through clay being of Permanent hardness, and that through chalk and limestone being of Temporary Hardness. Water originating from rain absorbed through peat or other organic matter will be Soft.
There is a link between Hardness and pH in that Hard water is either neutral (pH 7.0) or alkaline (above pH 7.0) and Soft water is acidic (below pH 7.0).