Marine Fish Water Quality Guide: Salinity, pH & Ammonia

Water quality management is one of the biggest challenges in marine fish keeping. Maintaining multiple parameters within proper ranges minimizes fish stress and maintains health.

Specific Gravity (Salinity)

One of the most important metrics in marine fish keeping.

• Target value: Specific gravity 1.020–1.025 (salinity 33–36ppt)
• Measurement methods: Hydrometer, refractometer, digital salinity meter
• Note: Evaporation raises specific gravity, so top off daily with RO/purified water
• Rapid specific gravity changes (more than 0.001/day) cause significant fish stress

pH (Acidity)

• Target value: pH 8.1–8.3
• Measurement methods: Test kit, digital pH meter
• Causes of pH drop: CO2 accumulation, organic decomposition, high biological density
• Solutions: Water changes, aeration, buffer additives

Nitrogen Cycle Management

Understanding the ammonia → nitrite → nitrate cycle is fundamental to tank management.

| Parameter | Target Value | Danger Level | |------|--------|----------| | Ammonia (NH3) | 0ppm | 0.25ppm+ | | Nitrite (NO2) | 0ppm | 0.5ppm+ | | Nitrate (NO3) | Below 10ppm | 50ppm+ |

Ammonia and nitrite levels spike after initial setup, so fish should only be introduced after water quality stabilizes.

Water Change Frequency and Method

• Regular maintenance: Change approximately 10–15% weekly
• Water change saltwater: Dissolve artificial salt mix in RO or purified water (tap water may contain excessive minerals)
• Pre-change acclimation: Match new saltwater temperature and specific gravity to tank before adding

Items to Check Regularly

• Daily: Water temperature, specific gravity, fish condition observation
• Weekly: pH, ammonia, nitrite
• Monthly: Nitrate, phosphate, alkalinity (KH)

Find Marine Fish on Bri-Choku

Welcoming healthy marine fish raised in stable water conditions is the shortcut to success. Find your ideal fish on Bri-Choku's marine fish category while consulting breeders about keeping conditions.