Free reef tank tool
Reef Salt Mix Calculator
Estimate how much reef salt mix you need to reach your target salinity for a new saltwater batch, water change, or salinity adjustment.
How the Reef Salt Mix Calculator Works
This reef salt mix calculator estimates the amount of dry reef salt mix needed to move a known water volume from a current salinity to a target salinity. It supports US gallons and liters, ppt and specific gravity, common salt mix presets, and a custom label value when your bucket gives its own mixing direction.
The result is an educational starting point. Salt mix formulas, humidity, measuring cups, temperature, incomplete dissolving, and calibration can change the final number. Always verify with your salt mix label and measure salinity after mixing.
Mixing New Saltwater from RO/DI
For a new saltwater batch, enter the water volume, set current salinity to 0 ppt, and choose your target. Many reef keepers mix close to 35 ppt, which is often around 1.026 specific gravity, but your exact target should match your system and livestock plan.
Raising Salinity in a Mixing Container
If the water is already mixed but reads low, enter the current salinity and the target salinity. The calculator estimates the extra dry salt mix needed for that container. Add less than the estimate at first, let it dissolve fully, then re-test and adjust gradually.
Water Change Batch Calculator
For a water change batch, calculate the salt needed for the new water before it reaches the aquarium. Match salinity and temperature before the water change, especially when corals or invertebrates are already in the tank.
Display Tank Salinity Adjustment
Do not add dry salt directly to a stocked display tank. For a salinity correction, prepare higher or lower salinity water outside the aquarium, make gradual water changes, re-test, and avoid rapid swings. Corals, fish, and invertebrates can react poorly to sudden salinity changes.
Related reef tools
Plan the next coral decision carefully.
Once salinity is stable, use these tools to check coral requirements, placement, light, flow, and compatibility before adding livestock.
Coral Identifier
Identify corals before buying or placing them.
Stable saltwater helps with reef setup. Coral Identifier helps when you are comparing a coral photo and need likely matches before checking care requirements.
Coral Identifier gives likely photo-based matches, not guaranteed IDs. Use the result as a starting point, then verify with trusted references before changing placement, light, or flow.
Reef Salt Mix Calculator FAQ
How much reef salt mix do I need per gallon?
A common rough starting point is about 132 grams, or about 4.7 ounces, per US gallon to reach around 35 ppt. Salt mixes vary, so verify the label and measure salinity after mixing.
How much salt mix do I need per liter?
Many reef salt mixes are roughly around 35 grams per liter at 35 ppt, but product formulas and measuring methods vary. Use the calculator as an estimate and check the salt mix label.
How much salt do I need to make 1.026 saltwater?
Specific gravity around 1.026 is close to 35 ppt for many reef references. The exact amount depends on water volume, current salinity, salt mix formula, temperature, and measurement calibration.
Can I add dry salt directly to my reef tank?
Do not add dry salt directly to a stocked aquarium with fish, corals, or invertebrates. Mix saltwater outside the display tank, let it dissolve, heat and aerate as needed, and measure salinity before use.
How do I raise salinity safely?
Raise salinity gradually. In a mixing container, add salt slowly and re-test. In a stocked display, prepare replacement water outside the tank and make gradual water changes rather than adding dry salt to the display.
What salinity should a reef tank be?
Many reef aquariums target around 35 ppt, often near 1.026 specific gravity, but acceptable targets depend on the system and livestock. Double-check your target if it is below 30 ppt or above 38 ppt.
Why does my measured salinity differ from the calculator?
Humidity, cup measurements, salt mix variation, incomplete dissolving, temperature, and refractometer or hydrometer calibration can all affect the final reading. Always measure after mixing.
More coral setup reading