Water Hardness
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<fishfyi-glossary slug="water-hardness"></fishfyi-glossary>Definition
A measure of dissolved mineral content (primarily calcium and magnesium) in aquarium water. Fish species have specific hardness preferences; mismatches cause stress and health issues.
Ausführliche Erklärung
Total hardness (GH — general hardness) measures calcium and magnesium concentrations, while carbonate hardness (KH — carbonate hardness or alkalinity) measures bicarbonate and carbonate ions that buffer against pH swings. Soft-water fish from the Amazon or Southeast Asian blackwater streams (discus, cardinal tetras, most dwarf cichlids) thrive at GH 1–5 dGH; African rift lake cichlids require GH 15–30 dGH and KH 10–20 dKH. Peat filtration and reverse osmosis lower hardness; crushed coral, aragonite substrate, and calcium carbonate additives raise it. Sudden hardness changes stress fish more than stable hardness outside the preferred range.