Salinity

What is it?
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulphates and bicarbonates.

It is typically expressed in the unit - parts per thousand (ppt) or approximately grams per litre. To measure this accurately in an aquarium you need to use a hydrometer or refractometer.

Links

 * Salinity on Wikipedia