Step-by-step
Step 1: Fill clean container with RODIUse a dedicated container - never one that held detergents or chemicals. Fill with RODI water (not tap, not bottled spring water).
Step 2: Heat to target tempAdd a small heater + powerhead. Heat to 78°F. Salt dissolves much faster in warm water.
Step 3: Add salt slowlyPour salt slowly into the moving water. Use approximately 0.5 cups (4 oz) per gallon for 1.025 SG. Use the salt-mix calculator at /calc/salt-mix/ for precise amounts by brand.
Step 4: Aerate 12-24 hoursRun powerhead constantly to fully dissolve and aerate the saltwater. CO2 dissipates during this time, raising pH to natural levels.
Step 5: Test salinityCalibrate refractometer with 35 ppt solution. Test mixed water - should read 1.025-1.026 SG. If low: add more salt. If high: add more RODI.
Step 6: Test temperature againMatch within 2°F of display tank before adding to the system. Cold water shocks coral.
Step 7: Use immediately or storeSalt water is ready to use. If storing: cap container, keep dark, use within 2 weeks. Long-term storage degrades trace elements.
Frequently asked questions
How long does saltwater take to mix?
12-24 hours with a powerhead. Adding salt + powerhead alone takes 1-2 hours to dissolve, but trace elements + pH stabilize over the full 24 hours.
Do I need RODI water for saltwater?
Yes, mandatory. Tap water has phosphate, copper, chloramines that fuel algae and kill coral. RODI = 0 TDS = predictable parameters.
Can I mix saltwater in the display tank?
NEVER for established systems with livestock. Salt creates massive pH/SG/temperature swings. Always mix in a separate container.