A stable (and correct) salinity is an important basis for successful reef aquariums. However, we often observe in our laboratory analyses that the salinity value deviates significantly from the optimal value. In order to guarantee a correct salinity in the reef aquarium, the measuring equipment should be continuously checked and also calibrated. Oceamo 35.0 ppt salinity reference was developed for the simple and safe calibration of refractometers. Because it is packaged in a resealable syringe, the reference is easy to use, extremely economical (only a few drops are needed) and has a very long shelf life.