S.G. Question?

[Jim]

I'm still kind of new ot reefing. I've been maintaing my specific gravity with an Instant Ocean hydrometer and trying to keep it at around 1.024. Recently I bought a refractometer and nulled it using both distilled water and RO ( same results at zero ) The S.G. was at 1.022, I cleaned my hydometer with vinegar and tested again and got 1.024 1/2. Which test should I stick with and if it's the refractometer should I raise my S.G.?

 

[NYreefNoob]

jim if ya want come by and dial it in off mine

 

[18oreefer]

I would go with the refractometer definatly. You could raise the S G but its not the end of the world at 022.

 

[MikeyZO]

Ive heard that zeroing in a refractometer with RO or distilled water will wind up with you getting an erroneous reading for your saltwater. Try getting a bottle of salinity calibration fluid like this
http://www.aquariumguys.com/salinityfluid.html

Zero it in using that, this way you will know its accurate for salinity. Also realize that refractometers measure salinity which is different from specific gravity. Salinity is the amount of salt dissolved in the water, specific gravity is the density of the water and is also temperature sensitive. So for instance, if you used your hydrometer and got your reading, and then let it sit for a few hours in a colder or warmer room, the reading would change. Refractometers therefore are more accurate because they measure the amount of salt that is dissolved and then give you a reading for salinity and a corresponding specific gravity for our tanks. Thats why most reefers use them over hydrometers.