fish.Favourable hardness values are not too high or too low.
Free chlorine(Cl2)
Free chlorine is a halogen chemical element,Concentrated levels of chlorine kill fish and aquatic life-forms. It is harmful to
fish, damaging their gills and skin.
Total Alkalinity&Carbonate (KH)
Total alkalinity measures the amount of alkaline substances (bicarbonate and carbonate) in your water. Ideal range is between
40-120 mg/L.Carbonate stabilizes pH in the water.If the KH drops below 40ppm,the pH will also start to drop.
pH
pH is measurement of acidity or alkalinity of fish water.
A pH value between 6.5 and 8.5 will be tolerated by most freshwater fish species. However, ideal pH ranges are species dependent.