Salinity is a very important parameter for a captive reef aquarium so it is essential to have a good quality salinity refractometer on hand to monitor levels on a constant basis. One option to consider is the Pro-1 Normal Seawater Refractometer from Tropic Eden. The folks at Tropic Eden are touting this tester as a highly precise and well built refractometer that is a quick and easy to use, whether it is for scientists out in the field or for saltwater aquarium hobbyists. The refractometer, which is packaged nicely, comes with a user manual, 2 pipettes, calibration key and pouch. It is an optical device that utilizes the refraction of light through transparent media to determine the salinity and specific gravity of the water being tested. It MORE