American Marine PINPOINT Salinity Monitor PINPOINT Salinity MonitorTM will as it should be and in an instant measure the volume of salt in any marine or freshwater system. The reading is fully temperature compensated and the conversion chart will precisely show the corresponding density (specific gravity) or % salt (refractometer) values. Each and every saltwater aquarist must own this monitor . the accuracy is very good! This monitor is particularly useful to decide the low level of salt required for Koi, whether or not in an aquarium or outside pond. Comes complete with meter, probe and calibration fluid.