Salinity

The Salinity (salt content) is a very misunderstood part to the success of a marine tank, as most people only top up with fresh water (RO water) once a week, making the environment very unstable by changing the water chemistry, as opposed to using a top-up system with a reservoir that tops up on a daily basis keeping the Salinity constant.

The strength of the salt water in your tank is measured in a number of different ways; this can be read with an electronic meter measuring in micro siemens as one of the most accurate forms of measurement. When measuring in micro siemens the reading should read 45 MS. One of the other forms used is a refractometer. This measures the salinity by using the refraction of light through a handheld device reading the salt content in parts per million. The reading here should read 1.025.

Then there are available the cheaper measuring instruments, for example one that floats on the water surface, with a marking marked in green or red. When floating in the tank the water line should be on the green or red line depending on whatever colour the hydrometer is. This is supposedly the correct salinity reading, but with my experience over the years has found these hydrometers totally in accurate.

As mentioned in the first paragraph what one doesn’t understand is salinity affects pH, alkalinity as well as a variety of other water chemistry readings.

One other important factor of maintaining salinity at 1025 determines the efficiency of the protein skimmer. If one runs the salinity to low the density of the water is reduced producing a less efficient skimmer.

Probably the most important factor of keeping the salinity constant is so that your fish and corals are able to adjust to the aquarium. As this is already a stressful environment for your corals and fish, without having to worry about the fluctuating of salinity. As in the ocean the salinity is kept totally stable. A fluctuating salinity indirectly causes disease to the fish due to stress, and the corals never settle and open to their full potential slowly deteriorating and finally ending up with a bacterial disease or a bristle worm infestation and finally death.