The new digital refractometer from Hanna Instruments is one svelte and highly accurate new electronic machine for testing the salinity of seawater. The $200 device is bileld as scientific and research grade: it may be overkill for many hobbyists but for the professional aquarist with more demanding testing needs, the Hanna Instruments seawater refractometer delivers more critical performance at a reasonable price. The digital refractometer measures salinity and automatically displays the concentration in PSU (practical salinity units), ppt (parts per thousand) and S.G., specific gravity. With features like temperature compensation, a waterproof case, battery power and calibration as easy as zeroing a weight scale, like the iPod this refractometer does one thing and it does it well. The Hanna Instruments seawater refractometer is available from Marine Depot for $199 + free shipping, click on the pdf link to see the full product release.