salinity and specific gravity?

bang guy

bang guy

Moderator
Salinity is the amount of salt in the water.
Specific Gravity is the density of the water.
The amount of salt in the water is the important measurement.
Given the Specific Gravity and the temperature you can look up what the Salinity is from a conversion chart.
 
bang guy

bang guy

Moderator
Absolutely. A Refractometer will directly measure the salinity without any conversion to look up. Just ignore the S.G. scale completely. The S.G. scale on refractometers isn't accurate anyway.
I recommend 35ppt for salinity if that matters.
 
lv-reefer

lv-reefer

Member
I have a plastic SeaTest Full Range Specific Gravity Water tester with the plastic floaty arm and I keep my specific gravity at 1.025 or salinity 34 ppt, is this good, or should I adjust so I'm at 1.026 / 35 ppt?? Water is 80 degrees.
 
007

007

Active Member
Bang Guy . . . .
On my refractometer, 35ppm is even with 1.025. However on another refractometer, the 35ppm is different. I dont remember which way, but I think it reads .024.
Anyway . . . should I be concerned about this? I have always measured based on .025 simply because it equates to .025
I guess I should compare against the other refractometer huh?
Is it common for the scales to be misadjusted?
 
kc36330

kc36330

Member
the equivilent should be 1.026 SG for a salinity of 35ppt.
FWIW the ocean on average is 35ppt and thats what i keep all my tanks at and have had great success with them for over 25 yrs now.
kc
 
bang guy

bang guy

Moderator

Originally posted by 007
Is it common for the scales to be misadjusted?
Both of them are right and both of them are wrong. That's why you should be using the Salinity scale and not the S.G. scale.
The refractometer measures Salinity, it cannot measure Specific Gravity nor do aquarium hobbiests need to know what the S.G. is.
 
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