Most refractometers used within the aquarium hobby are not specifically designed for reef aquariums and use an algorithm for the measurement of brine (NaCl – rather than seawater) at a temperature of 15°C / 59°F rather than 25°C / 77°F. Thus, a measurement deviation of up to 1.5ppt is possible, which can have a significant adverse effect on coral growth and colouration.

Main features of Red Sea’s Seawater Refractometer include:

• Directly reads the absolute salinity of seawater at 25°C / 77°F  ( No need for seawater or temperature compensation factors)
• Specifically designed for the ionic content of seawater (NSW) for more accurate salinity measurement (industry standard refractometers are calibrated for salt brine ).
• Calibrated for seawater (NSW) at 25°C / 77°F, the normal temperature range for reef aquariums
  (most standard refractometers are calibrated at of 15°C / 59°F ).
• Easier to read, higher resolution display, focussed to the relevant range for reef aquariums of up to 40ppt
• Includes Integrated Automatic  Temperature Compensation (ATC) for accurate measurement at standard ambient temperature.

Red Sea’s Refractometer display

The PPT scale on Red Sea’s Seawater refractometer is calculated using an algorithm for seawater and therefore will give a reading of the Absolute Salinity of seawater.

The PPT scale on regular salinity refractometers are calculated using an algorithm for Brine. Using a Brine refractometer for Seawater will give an error of approximately 1.5ppt in the salinity reading.