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What is Water Hardness?

The ‘Hardness’ of water is a measure of the amount of calcium carbonate (CaCO3) in the water. The hardness of tap water depends largely where in the UK you live. Very generally, the South East, East Midlands and Anglian areas have hard water (200mg/L + CaCO3 / 12°dH). The South West, West Midlands, Wales and the North West has much softer water, due to the underlying bedrock of these areas. If you need to know the water hardness, ask your water supplier or use a hardness test kit. Hard water does not harm freshwater fish, but the hardness may affect the dosage rate of some water treatments.