What is GH in aquariums?
GH (General Hardness) measures the concentration of dissolved minerals, mainly calcium and magnesium, in water.
Why GH matters
GH affects:
- Fish osmoregulation and bone development
- Invertebrate molting and shell formation
- Plant nutrient availability
Fish adapted to soft water may suffer in high GH, while hard-water species may struggle in low GH.
Typical GH ranges
- Soft water fish: 0–6 dGH
- Community tanks: 6–12 dGH
- Hard water fish: 12–20+ dGH
What influences GH
- Tap water source
- Rocks and substrates
- Mineral additives
- Water changes
GH is often evaluated alongside KH and pH for full water chemistry understanding.