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General Hardness
From The Aquarium Wiki
[edit] °GH - General Hardness
General, total or permanent hardness is a measure of the overall concentration of calcium, magnesium and other ions. It's measured in degrees, with one degree equal to about 17.9mg/l (17.86mg/l). The degree symbol is often replaced with a "d" (i.e. 6dGH or just 6dH). The harder the water, the higher the GH number.
- Some countries measure GH in ppm (like the USA), others use the German unit dH.
- Some countries use 'GCH' (General Carbonate Hardness) instead of 'GH'.
| Degrees | Parts Per Million | Description |
|---|---|---|
| 0 - 4 dH | 0 - 70 ppm | very soft |
| 4 - 8 dH | 70 - 140 ppm | soft |
| 8 - 12 dH | 140 - 210 ppm | medium hard |
| 12 - 18 dH | 210 - 320 ppm | fairly hard |
| 18 - 30 dH | 320 - 530 ppm | hard |
| Higher | > 530ppm | Liquid rock (Lake Malawi and Los Angeles, CA) |
[edit] Links
- See The Krib for more on this.
- Hardness: A Term with Many Meanings
