We recommend to prepare at least 15 litres (4 US gal) of saltwater. Mix your RO water with 585g (20.63 oz) of salt, and perform the test at least 2 hours after fully dissolved. Always check the salinity in which the test was made, as this will influence the measured parameters. A salinity refractometer is recommended, together with a calibration fluid. *Note that salinity readings also depend on the temperature. Please check your salinity at 20°C (68°F).

If you detect a small difference in parameters between your tank and the salt, the impact is also minor. For example if you make the typical recommended 10% water change, the change in parameters of your tank will only be 10% of the difference. If the Calcium level in your aquarium is 430ppm and the water change water is 450ppm, the difference is 20ppm. But as you are actually only changing 10% of aquarium volume, 10% of that 20ppm is only 2ppm. Changing water this way, with that discrepancy, would only result in a difference of 2ppm of Calcium. That’s 0.5%. E.g. Tank Ca = 430 ppm. New salt water Ca=450 ppm. The difference: 450-430 =20 ppm. Estimated impact: 10% *20 =2. Tank Ca after change will be 432ppm.