How Do I Mix Saltwater for My Reef Tank?

Properly mixed saltwater is the foundation of a healthy reef tank. Here's the step-by-step process for mixing saltwater that matches your tank's parameters.

What You'll Need

• RO/DI water (never use tap water)
• Quality reef salt mix (Red Sea, Instant Ocean Reef Crystals, etc.)
• Mixing container (food-safe bucket or brute trash can)
• Powerhead or pump for circulation
• Heater to match tank temperature
• Refractometer for measuring salinity

Step-by-Step Mixing Process

1. Fill with RO/DI water: Add the amount of purified water you need. Never use tap water—chlorine, chloramine, and heavy metals harm corals and fish.
2. Add salt gradually: Slowly add salt mix while the powerhead runs. Most salt mixes call for roughly 1/2 cup per gallon to hit 1.025.
3. Heat the water: Set your heater to match your display tank's temperature (typically 77-78°F).
4. Circulate and aerate: Let the powerhead run for at least 4-24 hours. This dissolves all solite and stabilizes pH.
5. Test salinity: Use a refractometer to confirm 1.025-1.026 specific gravity (35 ppt).
6. Test temperature: Ensure it matches your tank within 1-2°F before use.

Tips for Better Results

• Always add salt to water—never water to salt. Adding salt to water ensures proper dissolution.
• Mix at least 24 hours ahead for best results. Freshly mixed water can have unstable pH and alkalinity.
• Use a dedicated container that's never held chemicals or detergents.
• Store covered to prevent evaporation and contamination.
• Calibrate your refractometer regularly with calibration fluid.

Common Mistakes to Avoid

• Using tap water: Even dechlorinated tap water contains silicates, phosphates, and other contaminants that fuel algae.
• Not aerating: Freshly mixed water often has high CO2 and low pH—let it gas off.
• Incorrect temperature: Adding cold or hot water stresses livestock.
• Eyeballing salinity: Always measure with a calibrated refractometer.

Track your water change schedule and parameters with the ReefBay app to maintain consistency. Many successful reefers do weekly 10-15% water changes with properly mixed saltwater.