Refractometer vs hydrometer

[coralfishreef]

A friendly reminder to check your Sg / Salinity.

I haven’t checked Sg in a couple of weeks. I normally keep the Sg between 1.026 to 1.0265. My main display tank is fed a lot of frozen and liquid food and Sg creeps up over time. Sg was reading 1.0272 - 1.0274 according to the TM Precision hydrometer.

Some different instruments for comparison.

$125 Milwaukee digital refractometer. This was calibrated a year or two ago and hasn’t needed calibration since, but it also has been barely used. The reading has always been accurate, but I don’t use this because the reading accuracy is +\- .002.


$35 BRS refractometer. This had to be recalibrated tonight. The initial reading was off by .001 - .0015.



$35 TM High Precision Refractometer. Only used to calibrate the refractometer.


$10? Hydrometer from Amazon. I received a good one that is accurate but the scale is difficult to read. I don’t use this because of this.


$10 Swing arm. Still needs 24 hours to “season” the needle, but it’s looking pretty good.

 

[BiGGiePauls33]

Plus 1 on this, unfortunately I smoked quite a few high end pieces by not checking and calibrating probes. Now I check S.G. with a hydrometer as they've been consistent.

 

[thrillreefer]

I could use an analytical balance at work to weigh e.g. 1 mL tank water and then convert density to salinity right? Might be a good way to check calibration of my cheap swing arm hydrometer. Never done that but now I kinda want to

 

[coralfishreef]

I could use an analytical balance at work to weigh e.g. 1 mL tank water and then convert density to salinity right? Might be a good way to check calibration of my cheap swing arm hydrometer. Never done that but now I kinda want to

Did a search and found this thread. This looks interesting and fun.

Salinity determination by density

The subject of various alternative means of determining salinity previously came up in this thread where I dabbled (in what I now see was an amusingly over-simplified way) with the idea of using a couple of simple tools to determine salinity by calculating the density of your tank water. I have...

www.reef2reef.com

 

[coralfishreef]

New Sg readings after removing a couple gallons of saltwater and 24 hours of “seasoning” the swing arm. What exactly does it mean to “season” the needle?

Milwaukee digital refractometer, 1.027


BRS refractometer, just under 1.028. Calibration is slightly off again, or calibration error from yesterday, or maybe an issue with the temperature. This is okay, because I prefer having the reading show on the higher side since the tank runs on the higher end of the safe range. I’ll have to check the calibration again.


TM High Precision hydrometer, 1.0267 - 1.0268


Plastic swing-arm hydrometer, just under 1.028