SEAWATER Refractometer from DD Aquarium
What is the difference between our NEW refractometer and others you may ask?
Nearly all, if not all, of the refractometers currently available to the aquarium hobby are designed to measure saltwater (sodium chloride or brine solution) and not ‘seawater’.
Although seawater is mainly composed of sodium chloride, it also contains other elements such as magnesium and calcium which will slightly change the refractive index and give a slightly different result.
The most common symptom of this difference in refractive index can be seen when mixing salt as salt instructions per manufacturer and reaching a solution for the power where it appears, through tests, that the levels of elements are lower than indicated by the manufacturer.
In fact all levels are low if the salinity is not as high as the aquarist thinks – we have all seen low Ca or Mg for a given SG with virtually all brands of salt.
It turns out that a 35ppt solution of real seawater has the same refractive index as a 36.5ppt solution of brine and so when using a brine/salt refractometer the salinity is likely to be low by 1.5ppt. This can be allowed for the aquarist, but only if they are aware of the difference.
After extensive development, new refractometer DD addresses this issue, giving true salinity results when correctly calibrated (using osmosis water) and greater accuracy than previously achievable.
True calibration for Seawater measurement. A new finer scale ranging from 20-40ppt salinity (SG 1.015 to 1.030) 20/20 calibration at room temperature for greater consistency and accuracy in everyday use. Full ATC (automatic temperature compensation) ranging from 5 to 30°C.
** Calibration with osmosis water, manual is under foam rubber in the lid**