Salinity Refractometer for Aquarium, Seawater and Food with Automatic Temperature Compensation and Dual Scale (Salinity 0-100&permil; & Refractive Index of 1.0 - 1.070 S.g.) By Water Solutions Measure salt water or salinity of water, ideal for aquariums and marine monitoring. Measures on 2 scales, Specific Gravity (D 20/20) and parts per thousand (). Features automatic temperature compensation. Comes with hard case, dropper, screwdriver and cleaning cloth. No need salinity calibration fluid,it has been calibrated well.