A refractometer measures reflective index. Manufactures stick a couple scales(specific gravity/SG or salinity) for you to see the levels easily. Reflective index, SG and salinity can be converted from one to other (with a small error that can be ignored for our aquarium use). If your refractometer says automatic temperature compensate (ATC), it means the reflective index level is being compensated.
I usually look at salinity because it's easy for me to see 35 ppt (salinity) than 1.0264(SG) on my refractometer.
Last edited by George; 02-08-2014 at 10:41 PM.
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