Glossary

salinity

General term for the salt concentration of water.

Used in 17 species profiles

automatic top off
Automated system for adding water to an aquarium or sump in order to maintain a constant water volume. Particularly important in marine aquaria where salinity increases if water is allowed to evaporate without being replaced.
brackish
Refers to water with a salinity between that of freshwater and seawater, technically 0.5 - 30 grams of salt per litre, equivalent to 0.5 - 30 parts per thousand (ppt).
euryhaline
Of aquatic organisms, able to tolerate a wide range of salinity. Opposite of stenohaline.
hypersaline
Used in reference to bodies of water with a higher salinity than sea water.
refractometer
Instrument used to measure salinity or specific gravity via the refractive index (basically, the degree that light bends when shined through something) of a liquid. Most models are designed to measure sodium chloride or brine solutions and not seawater which contains a more complex range of salts and minerals, but usually more accurate than a hydrometer nevertheless.
specific gravity
Ratio of the density of a liquid to the density compared with pure water. Often used to deduce the salinity of aquarium water and measured using a hydrometer or refractometer.