Hard Water

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How to Be Sure: Understanding Aquarium Water Hardness (GH & KH)

GH (General Hardness): 14 °dH | KH (Carbonate Hardness): 10-15 °dH
Water Hardness Level: HARD – This hardness level is generally suitable for most community aquarium fish. It’s ideal for alkaliphiles (alkaline-loving species), such as African lake cichlids.

GH: 28+ °dH | KH: 20+ °dH
Water Hardness Level: VERY HARD – Water this hard is usually too harsh for most aquarium fish and can cause health issues if not managed properly.

What is Water Hardness?

Water hardness measures the total dissolved salts in aquarium water, mainly calcium and magnesium ions. Calcium is the most influential mineral affecting hardness. These ions occur mostly as hydroxides, carbonates, or bicarbonates.

  • General Hardness (GH): Total amount of dissolved calcium and magnesium salts.
  • Carbonate Hardness (KH): Portion of hardness from carbonates and bicarbonates, which can be reduced by boiling water.
  • Permanent Hardness: The remaining hardness after boiling, which cannot be removed easily.

Step 1 – Treat Your Aquarium Water

  • To reduce high hardness levels, perform several small water changes using reverse osmosis (RO) water or rainwater.
  • If RO water isn’t available, boiled tap water can help lower carbonate hardness by removing KH.

Step 2 – Support Your Fish

  • Use Aqualibrium First Aid Salt to help your fish cope with stress caused by changes in water hardness.
  • If your fish are gasping at the surface, increase oxygen levels by adding an air pump or air stone to improve aeration.

Maintaining the right water hardness ensures a healthy environment for your aquarium fish, improving their well-being and longevity.