I would not recommend this refractometer unless you already have it.
It is trying to measure too wide of a range and so has inadequate sensitivity/accuracy, IMO. It can work, and is probably as good as a cheap refractometer.
It has a stated accuracy of +/- 0.2 % Brix. See below, translating that to +/- 1 ppt.
Title photo by R2R member Rskillz By Randy Holmes-Farley Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions Read more here...
www.reefedition.com
Brix Refractometers
A commonly manufactured type of refractometer is called a Brix refractometer. Its scale usually reads in Brix, or % Brix (percent Brix). These refractometers are used in many industries to measure the concentration of sugar in water such as in the soft drink industry. They can be used to measure seawater’s salinity, but are not always precise enough around the range of seawater’s refractive index to be useful. A resolution of 0.2% Brix is common, and that is borderline acceptable for the reasons detailed below.
Table 4 shows the relationship between seawater salinity, refractive index and % Brix. If a refractometer has a resolution (not accuracy, but resolution, which is the finest amount it can distinguish) of 0.2 % Brix, then that translates to about +/- 1 ppt. So the best resolution would translate to 35 ppt seawater reading 34-36 ppt, which may be adequate for reef aquarists. A Brix refractometer that reads 0 to 10 % Brix with a resolution of 0.1% Brix might be a fine choice for determining seawater salinity in a reef aquarium, (although they are not inexpensive). Some Brix refractometers have a resolution of 0.5 % Brix or even 1% Brix, and they would not be suitable choices.
