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Aquarium Advice Freak
Jul 19, 2004
I got my new portable refractometer in the mail today. I used it to measure specific gravity and it is measuring almost 1.030! My hydronomer is only measuring 1.023. Which should i trust? Would this high salinity effect the fish and how?

By the way, I DID calibrate the refractometer
my SG was tested with the same refractometer and was also high, but my hydronometer said it was just right. so, if the refractometer is always right, does that mean that hydronometers are always wrong?
Hey I get my water from the ocean and when i use the hydrometer to check it says 1.023. That means myne must be right.
Not necessarily. It may be correct today and not tomorrow or even 10 minutes from now. Then again it may be correct all the time. Check the same sample with a calibrated refactometer and you'll know for sure.

BTW, the ocean does not have a 1.023 SG everywhere. Different oceans have different SGs and it varies from day to day....

Check out this article.
"Different oceans have slightly different specific gravities. The tropical Indo-Pacific has an average specific gravity of 1.022 - 1.025. The Caribbean has an average specific gravity of 1.023 - 1.026. The Red Sea has an average specific gravity of 1.028 - 1.035. The specific gravity changes in each area are due largely to rain fall."
cmor is right, there are places that get some rain, and there are places that get NO rain, which would result in vaperation, and having the salinity rise, and when it rains alot, the salinity will lower, since there is no salt in fresh water :wink:
I'm almost certain i calibrated it correctly but just to make sure I want to ask. I measured a sample of RO/DI water and it read 1 SG. So i knew it was calibrated. Correct?
Did you get a solution with it to calibrate it to?
Mine came with a bottle that should read right at 30.
RO/DI should really read 0.
if you don't have a solution then RO/DI water is perfectly fine to use. It should be at exactly 1. Be sure to follow the refractometer's directions. Hydrometers are notoriously bad at giving different results. due to salt build up, bubbles, net setting it on a perfectly level surface, etc. Trust the refractometer.
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