Measuring Salinity / Specific Gravity in Aquariums

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Randy Holmes-Farley

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I found the salinity correction charts inaccurate, especially if the temp is not close to the temp the hydrometer was calibrated.
Have you tried checking the chart for accuracy?

Hydrometer temperature correction tables are not the same corrections that would be needed for a non ATC refractometer.

Anyone thinking they need a correction table can always check for themselves if it is correct by testing the same water at multiple temperatures and see whether the salinity changes (it should not).
 
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Jay Hemdal

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This is the first time I have utilised NSW directly from the reef here.. i checked the SG from collected water and its only 1.020..I was a bit surprised by this..Hmmm?

Was it collected near shore or after a heavy rain? Most offshore NSW will read 1.024 to 1.026 specific gravity units. If you got your water from offshore, then I would suspect that your measuring device isn't accurate. One way to confirm that is to measure it with some other device to see if they agree.

Jay
 

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Hydrometer temperature correction tables are not the same corrections that would be needed for a non ATC refractometer.

Anyone thinking they need a correction table can always check for themselves if it is correct by testing the same water at multiple temperatures and see whether the salinity changes (it should not).
Not sure if I knew that or not but I was referring to the hydrometer salinity correction charts, when using a hydrometer, maybe the one I use is incorrect, I have checked it, don’t get the same results if I heat the water to the correct calibrated temp (I use a certified thermometer to 0.1c) here it is if you want to give it the once over?

 

KStatefan

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Not sure if I knew that or not but I was referring to the hydrometer salinity correction charts, when using a hydrometer, maybe the one I use is incorrect, I have checked it, don’t get the same results if I heat the water to the correct calibrated temp (I use a certified thermometer to 0.1c) here it is if you want to give it the once over?


That calculator gives close to the same results as Randy's formula of 0.00019 per 1° F. I would guess the difference is just rounding error. Average difference for my last couple months was -0.000090 S.G.
 

Lee adams

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Was it collected near shore or after a heavy rain? Most offshore NSW will read 1.024 to 1.026 specific gravity units. If you got your water from offshore, then I would suspect that your measuring device isn't accurate. One way to confirm that is to measure it with some other device to see if they agree.

Jay
We take the water from around 10 meters from shore which is already reef..As a wine producer hobbyist,I know how to use a hydrometer!
I was also surprised but it is what it is I guess.
 
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