SG or Salinity?

[Oscar]

I am a little confused. Most people on this board and other boards make reference to SG but rarely mention salinity when discussing their water parameters.

Isn't specific gravity just a substitute for salinity? If you know your specific gravity AND temperature then you can calculate your salinity. Quoting SG on its own is meaningless. Isn't it?

I have been tracking salinity and not SG. Although I also record water temperature as well.

[sphelps]

SG, specific gravity is a ratio of density compared to pure water. Seawater has a density of around 1025 kg/m^3 and pure water is around 1000kg/m^3 and therefore the seawater has a SG of 1.025. Density changes with temperature but since it's a ratio of two densities it has little effect.

SG seems to be the standard and it may make more sense to use salinity but it also makes more sense to use mm over inches since it would be more accurate but people are just more familiar with inches, for example my tank is 914 x 914 x 610 mm

[Oscar]

OK, just one of those standards that has stuck. Who really measures their weight in kg, height in cm or air pressure in kilo pascals anyway?

[brizzo]

Originally Posted by Oscar

Who really measures their weight in kg, height in cm or air pressure in kilo pascals anyway?

sphelps the engineer!

[Chin_Lee]

Originally Posted by sphelps

SG, specific gravity is a ratio of density compared to pure water. Seawater has a density of around 1025 kg/m^3 and pure water is around 1000kg/m^3 and therefore the seawater has a SG of 1.025. Density changes with temperature but since it's a ratio of two densities it has little effect.

SG seems to be the standard and it may make more sense to use salinity but it also makes more sense to use mm over inches since it would be more accurate but people are just more familiar with inches, for example my tank is 914 x 914 x 610 mm

Shelps you kill me with that Greek but I love it. So concise yet so mystical.