Conductance and Salinity

Conductance is described by the sum of all the dissolved salts in water. The more salts that are dissolved in the water, the better the conductivity. Demineralized water will have hardly any electricity. In particular, conductance plays a role if soft-water fish are to be bred.

Salinity and redox (oxidation-reduction) potential
A determination of the salinity and the redox potential is only required for brackish and marine water aquariums.
The density of the salt content is measured with a hydrometer. Fresh water is at a temperature of 4 degrees Celsius, and has a specific gravity of 1.0.

Tropical sea water, which is usually modeled in a seawater aquarium, however, because of the dissolved salts and trace elements, has at this temperature a specific gravity of from 1.020 to 1.027. Brackish water is between these two values. The hydrometers used in aquarium are calibrated at 24 degrees Celsius.

The redox potential (rH-value) tells you how much charge the water with organic matter has and the oxygen content of it. High values indicate high oxygen content and tend toward a low content of organic matter. Electronic measuring instruments can be used to measure the rH value. In determining the values, the pH value and the water temperature must be considered.