Understanding Water Parameters — pH, GH, KH
Master aquarium water chemistry. Learn what pH, GH, and KH mean, how to test, and how to match fish to your water.
wasserwerte · 6 Min. Lesezeit · water chemistry, pH, GH, KH, testing
Understanding Water Parameters — pH, GH, KH
Water chemistry can seem intimidating, but understanding these three key parameters will dramatically improve your success rate.
pH — Acidity/Alkalinity Scale
pH measures how acidic or alkaline your water is, ranging from 0 (very acidic) to 14 (very alkaline). Aquarium pH typically sits between 6.0-8.5.
pH Ranges by Fish Type:
- Acidic (6.0-7.0): Tetras, Discus, many South American species
- Neutral (7.0): Most community fish tolerate this well
- Alkaline (7.5-8.5): African cichlids, livebearers, goldfish
Stability matters more than perfection! A stable pH of 7.5 is better than constantly fluctuating between 6.5-7.5.
What Affects pH?
- CO2 levels (higher CO2 = lower pH)
- KH (carbonate hardness) buffers pH
- Driftwood/peat lowers pH
- Crushed coral/limestone raises pH
GH — General Hardness
GH measures dissolved minerals, mainly calcium and magnesium. Measured in degrees (°dH or ppm).
GH Categories:
- Soft (0-6°dH / 0-100ppm): Discus, tetras, Amazonian species
- Moderate (6-12°dH / 100-200ppm): Most community fish
- Hard (12-18°dH / 200-300ppm): Livebearers, some cichlids
- Very hard (18+°dH / 300+ppm): African rift lake cichlids
Fish evolved in specific hardness ranges. Soft-water fish stressed in hard water can suffer immune problems, and vice versa.
KH — Carbonate Hardness
KH measures carbonate and bicarbonate, which buffer your pH and prevent dangerous swings.
Why KH Matters:
- Low KH (<3°dH): pH can crash suddenly
- Moderate KH (3-8°dH): Stable pH in most tanks
- High KH (>8°dH): Very stable pH, hard to adjust
KH is your stability safety net. Even with CO2 injection, sufficient KH prevents pH from dropping too fast.
Testing Your Water
Essential Tests:
- API Master Test Kit (liquid, not strips!)
- Tests: Ammonia, Nitrite, Nitrate, pH, GH/KH
Frequency:
- Cycling stage: Daily
- First 3 months: Weekly
- Established tank: Monthly or when issues arise
How to Test:
- Use clean, dry test tubes
- Follow instructions exactly (drop counts matter!)
- Read results in good lighting
- Log results to track trends
Adjusting Water Parameters
Golden Rule: Stability > Perfection
Gradual changes only! Rapid swings shock and kill fish.
Lowering pH/GH/KH:
- Mix RO/DI water with tap (50/50 blend)
- Add driftwood (slow, natural)
- Peat in filter (tints water)
- Indian almond leaves
Raising pH/GH/KH:
- Add crushed coral to filter
- Limestone rocks in tank
- Alkaline buffer products
- Baking soda (KH) or calcium chloride (GH)
Never adjust parameters with fish in tank! Prepare water in buckets before water changes.
Matching Fish to Your Water
The easiest approach: Choose fish suited to your tap water!
If You Have Hard Alkaline Water:
- Livebearers (Guppies, Mollies, Platies)
- African Cichlids (Malawi, Tanganyika)
- Goldfish
- Rainbowfish
If You Have Soft Acidic Water:
- Tetras (Neon, Cardinal, Rummy-nose)
- Discus
- Apistogramma
- Rasboras
Conclusion
Test, log, and understand your baseline water chemistry. Then stock fish that thrive in those conditions rather than fighting to alter parameters.
Stable water = healthy fish = happy aquarist!
Weitere Artikel