How to Be Sure: Understanding Soft Aquarium Water Hardness (GH & KH)
GH (General Hardness): 0 °dH | KH (Carbonate Hardness): 0 °dH
Water Hardness Level: VERY SOFT – Water this soft is generally too soft for most aquarium fish and can lead to unstable water conditions.
GH: 3-7 °dH | KH: 3-6 °dH
Water Hardness Level: SOFT – This hardness range is typically acceptable for most community fish and is ideal for acidophiles (acid-loving fish) like neon tetras.
What is Water Hardness and Why Does It Matter?
Water hardness measures the total dissolved salts in aquarium water, primarily calcium and magnesium ions, with calcium being the most significant. These minerals exist mostly as hydroxides, carbonates, or bicarbonates.
- General Hardness (GH): The total concentration of calcium and magnesium salts.
- Carbonate Hardness (KH): The carbonate and bicarbonate portion of hardness, which helps buffer aquarium pH and can be reduced by boiling water.
- Permanent Hardness: The portion of hardness that remains after boiling and cannot be removed easily.
A stable KH level is crucial to maintaining a steady pH, as it buffers against acidification caused by nitrification and respiration. Low KH levels can cause dangerous pH swings, negatively impacting fish health. Water hardness also influences fish osmoregulation, blood pH, kidney function, and egg development.
Step 1 – Adjust Your Aquarium Water Hardness
- To increase hardness, add commercial KH salts or perform water changes using tap water with higher mineral content.
- Alternatively, adding crushed coral or limestone to your aquarium can naturally raise KH and GH levels.
Step 2 – Support Your Fish During Hardness Adjustments
- Use Aqualibrium First Aid Salt to help your fish cope with stress caused by changes in water hardness.
- If you notice fish gasping at the surface, increase oxygen levels by adding an air pump or air stone to improve aeration.
Maintaining proper water hardness ensures a healthy and stable environment for your aquarium fish, promoting their overall well-being and vitality.