Understanding Water Parameters
pH, GH, KH, ammonia, nitrite, nitrate — what they mean and why they matter.
Water chemistry is the invisible foundation of every aquarium. Understanding these numbers is the difference between fish that survive and fish that thrive.
pH — Acidity / Alkalinity
Measured on a scale of 0-14. Most freshwater fish do well in 6.5-7.5. African cichlids prefer 7.5-8.5. Blackwater species want 5.5-6.5. Stability matters more than hitting an exact number — gradual shifts are fine, sudden swings are deadly.
GH — General Hardness
Measures dissolved calcium and magnesium. Soft water (1-4 dGH) suits most South American fish. Hard water (8-15 dGH) suits African cichlids and livebearers. Plants need at least 3-4 dGH for calcium uptake.
KH — Carbonate Hardness
Your pH buffer. Higher KH prevents pH swings. Low KH = unstable pH (risky). Most planted tanks do well at 2-5 dKH. If injecting CO₂, maintain at least 1-2 dKH to prevent dangerous pH drops overnight.
The Nitrogen Cycle: Ammonia → Nitrite → Nitrate
Ammonia (NH₃) — toxic. Produced by fish waste and decomposing food. Should always read 0ppm in a cycled tank. If it's not zero, do an immediate water change. Nitrite (NO₂) — also toxic. Produced as bacteria convert ammonia. Should also be 0ppm in a cycled tank. Nitrate (NO₃) — relatively harmless at low levels. The end product of the nitrogen cycle. Keep below 40ppm with regular water changes. Plants consume nitrate, so heavily planted tanks often read 0-10ppm naturally.
