Red Sea’s Seawater Refractometer offers exceptional accuracy, for measuring the absolute salinity of seawater at a temperature of 25^oC/77⁰F.

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) and at a temperature of 15^oC/59 ⁰F rather than 25^oC/77 ⁰F. Thus, a measurement deviation of up to 1.5ppt is possible, which can have a significant adverse effect on coral growth and coloration.