Apex Salinity Probe vs ATC Refractometer

[SereneAquatic]

We have our new tank filled and are trying to level out the salinity to as close as possible on 35. The Salinity probe for the Apex is saying 34.1, but the refractometer is showing about 31. (Just slightly above 30, nowhere near 35). I calibrated the refractometer immediately prior to use, even waiting the suggested 45 seconds for calibration.

Which one should I trust? Do I average the two? I expected them to be closer... somebody is lying... :frog:

 

[nereefpat]

I would trust the properly calibrated refractometer, and then use the probe to monitor stability.

Did you calibrate the probe?

 

[SereneAquatic]

I can't remember which ones had to be calibrated and which did not. The manual is out of date when I try to look at the probe calibration (they dont even mention sending the other two probes aside from ORP and pH). I think it was only these two that came with calibration solution, the other two said that they are already calibrated.

 

[rocsec1]

The probe has to be calibrated. I use mine to keep an on the water in the tank. Is it stable? I use my Hanna to test mixed water.

 

[der_wille_zur_macht]

I'd trust a properly calibrated and properly used refractometer over an electronic meter of unknown state any day.

 

[Cheapreef]

As others stated go with the calibrated Refractometer reading. You have to calibrate the salinity probe very carefully making sure there are absolutely no bubbles and temp matched calibration solition. It took me 3 times to get mine 100% calibrated to the refactometer reading, now it is within .1-.3 throughout the day.

 

[Xandernfs]

I had to recalibrate my probe. I kept getting false reading (37+) when the actual salinity was 31. I was also getting 28 during water changes because I think air bubbles were getting trapped on the sensor causing it to read low....thats just a guess. I have yet to recalibrate the probe, but when I do I'm going to buy multiple packets of calibration fluid since it's so cheap. Bottom line, I trust my refractometer over the probe any day.