The Seawater Salinity Refractometer is a must-have for any saltwater aquarium or pool. This refractometer features automatic temperature compensation so it will always give you the most accurate measurement of salinity in your water. With a measuring range of 0-100, this refractometer is perfect for use with saltwater fish or for checking the salinity of freshwater springs. The minimum scale is 1, which means you can be confident in your measurement results. The resolution is 1, which means you can be confident in your measurement results.