How do I measure the salinity of the water?
The salinity of saltwater can be manually measured using many instruments. The least expensive option is to use a hydrometer. A hydrometer is usually a clear plastic container with a floating needle inside. DO NOT USE THIS!!! It is notorious for giving inaccurate readings. You can also measure the salinity using a refractometer. Refractometers are usually a little more than twice the cost of a hydrometer but well worth the added price when considering accuracy. Make sure to also purchase a calibration solution as it is not as accurate to calibrate with RO/DI water as many directions suggest. The science behind the calibration fluid is that you are reading saltwater, which is considered in the high range of a refractometer. When using RODI water to calibrate and make a small error on a low range calibration, that error is magnified when reading a high range result. There are also probes and other automated ways to test your salinity if you are looking for a more hands off approach but like refractometers need to be calibrated regularly with their own specific calibration fluids that are readily available.