Water hardness is mainly affected by the substrate. To know the hardness, metallic ions present in the water are measured, particularly calcium and then magnesium.
Elements such as calcium and magnesium that raise hardness may be present in rocks of calcareous origin. To learn how to recognize a rock of limestone origin and learn about which rocks are suitable for use in aquariums visit thefollowing link:
In any trade specializing in aquarianism we can get dH meters.
The graph shows how water is described by the influence of calcium carbonate present in the water.
Up to 3° is considered soft water, between 3 and 6° moderately soft, between 6 and 12° slightly hard, between 12 and 18° moderately hard, between 18 and 25° hard and more than 25° very hard.
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