KH (Carbonate Hardness)

KH measures carbonate and bicarbonate levels in water and determines how stable pH remains in an aquarium.

What is KH in aquariums?

KH (Carbonate Hardness) represents the buffering capacity of water, helping resist sudden pH changes.

Why KH is important

Low KH can cause dangerous pH swings, while high KH stabilizes alkaline environments.

Typical KH ranges

  • Soft water tanks: 0–3 dKH
  • Community tanks: 3–6 dKH
  • African cichlids / marine: 7–12+ dKH

What affects KH

  • Tap water composition
  • Crushed coral or limestone
  • Water changes
  • Biological activity

KH directly influences pH stability and should be monitored regularly.