Tropical Fish Water Quality Basics: pH, Hardness & Nitrogen Cycle

Water quality management is the deciding factor in tropical fish keeping success. Even clear-looking water can contain invisible chemicals harmful to fish. Learn the basics of water chemistry to keep your fish healthy for years to come.

pH Basics

pH is an indicator of water acidity or alkalinity, measured on a scale of 0-14, with 7 being neutral.

• Acidic: Below pH 7. Preferred by Amazonian fish (Neon Tetras, Discus, etc.)
• Neutral to slightly alkaline: pH 7-7.5. Suitable for Guppies, Platies, Corydoras, etc.
• Alkaline: Above pH 7.5. Required for African Cichlids and similar species

Ideal pH (general guideline for tropical fish): 6.5-7.5

Rapid pH changes cause pH shock, which can be fatal. Limit water changes to about 1/3 of the tank volume at a time.

GH and KH (Hardness) Basics

• GH (General Hardness): Measures calcium and magnesium ion content, indicating water "hardness"
• KH (Carbonate Hardness): Related to pH stability (buffering capacity)

Soft water fish (Tetras, Bettas) prefer low GH, while hard water fish (African Cichlids) prefer high GH. Tap water hardness varies significantly by region.

Nitrogen Cycle and Harmful Substances

Fish waste and uneaten food decompose through the cycle: Ammonia -> Nitrite -> Nitrate.

| Substance | Toxicity | Solution | |-----------|----------|----------| | Ammonia | Very high | Broken down by filter bacteria | | Nitrite | High | Converted to nitrate by bacteria | | Nitrate | Relatively low | Diluted through water changes |

Newly set up tanks lack beneficial bacteria, causing ammonia and nitrite to spike. Run the filter for 2-4 weeks before adding fish to establish bacterial colonies (using the pilot fish method or fishless cycling).

Water Testing Methods

Regular water testing is fundamental to health management.

Testing Methods - Liquid reagent type: High accuracy. Can individually measure pH, ammonia, nitrite, and nitrate - Test strip type: Quick and convenient. Can check multiple parameters at once but with lower accuracy

Recommended Testing Frequency - Initial setup period: Daily to every 2 days - After stabilization: About once per week - When problems are suspected: Test immediately

Welcome Your Tropical Fish from Bri-Choku

On Bri-Choku, you can purchase tropical fish raised under proper water quality management directly from specialist breeders. Asking breeders about their water quality parameters before purchase ensures a smooth transition for your new fish.