Understanding pH, GH and KH in Your Aquarium
By Melbourne Tropical Team ยท 1 min read
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Demystifying pH, general hardness and carbonate hardness, and how to match them to your fish.
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The three measures of water chemistry
pH measures acidity; GH (general hardness) measures dissolved calcium and magnesium; KH (carbonate hardness) measures buffering capacity that keeps pH stable.
Why they matter
Different fish evolved for different water. Livebearers love hard, alkaline water; many tetras and rams prefer soft, acidic water. Stable parameters matter more than chasing a perfect number. Convert your readings with our parameter converter.
Adjusting safely
Change parameters slowly and only when necessary. Stable, slightly-wrong water is healthier than constantly fluctuating 'perfect' water.
Frequently Asked Questions
Should I adjust my aquarium pH?
Usually no. Most fish adapt to stable water. Chasing pH causes dangerous swings โ choose fish that suit your tap water instead.
What is the difference between GH and KH?
GH measures calcium and magnesium (general hardness); KH measures carbonate buffering that stabilises pH.