Water Hardness Converter

All biology tools

Convert between German degrees (dGH), ppm, and mmol/L accurately.

Hardness Input

Hardness Value

Input Unit

Conversion Results

German Degrees10.00°dH

Parts Per Million178.5mg/L

Molar Concentration1.783mmol/L

Hardness Scale (°dH)

Water Classification

Based on general hardness level.

About this calculator

Understanding Water Hardness

General Hardness (GH) refers to the concentration of dissolved divalent metal ions, primarily calcium and magnesium. It's often measured in German Degrees (°dH) or ppm (parts per million). Different aquatic species have specific hardness requirements for proper health, growth, and reproduction.

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Pro Tips

Species Specific: Softwater fish like Discus prefer low dGH (0-4), while African Cichlids thrive in hard water (12-20+).
KH vs GH: Remember that GH measures mineral content, while KH (Carbonate Hardness) measures the water's buffering capacity.
Inverts: Shrimp and snails require some hardness (specifically calcium) to build their shells/exoskeletons.
Evaporation: When water evaporates, minerals stay behind, gradually increasing hardness. Regular water changes help stabilize this.

Fun Facts

"1 dGH is defined as 10 mg of calcium oxide (CaO) per liter of water."
"Very hard water can lead to 'limescale' buildup on aquarium equipment and glass lids."
"Rainwater is naturally soft, while groundwater in limestone-rich areas is very hard."

Formula: 1 dGH ≈ 17.85 ppm ≈ 0.178 mmol/L