Salinity with refractometer vs probe, what to trust?

[balajeek15]

I have new version of Neptune Apex controller setup and it shows the salinity is 35+ but with refractometer it shows 1.020, which one should i trust.?

Spoke with neptune CS and they say their probe reading may not match with other salinity testers, they helped with the calibration and setup. Its been like that for months and i happen to test again yesterday and still there is that discrepancy.

On my QT i always have the 1.025 salinity which most LFS have and i am little concerned when transferring from QT to DT.

 

[link81]

whens the last time you calibrated the refractometer? it might be off a couple points.

 

[balajeek15]

whens the last time you calibrated the refractometer? it might be off a couple points.

when initially setup 8 months ago

 

[Daniel91]

Calibrate it, then test again.
I also suggest calibrating it regularly moving forward.

 

[balajeek15]

Calibrate it, then test again.
I also suggest calibrating it regularly moving forward.

How often it need to be calibrated, what about other probes like PH, Temp and ORP?

 

[Daniel91]

I am talking about the refractometer. I would calibrate once a month. People might do it more often or never, so it’s a personal preference

 

[link81]

i zero mine out every few months with ro/di.
i really need to get cal solution also to set it to 35.

 

[balajeek15]

I am talking about the refractometer. I would calibrate once a month. People might do it more often or never, so it’s a personal preference

Oh my bad, will try tonight. Thanks.

 

[balajeek15]

i zero mine out every few months with ro/di.
i really need to get cal solution also to set it to 35.

what cal solution you used, any link?

 

[KStatefan]

http://www.reefkeeping.com/issues/2004-06/rhf/index.php

 

[ca1ore]

I would believe a calibrated, good quality refractometer over the apex salinity probe every time. I use the latter, but only for directional changes not for absolute levels.

 

[link81]

ive never actually bought a standard. i should.....

what cal solution you used, any link?

 

[link81]

I wonder if you can use the same calibration standard for both the probe and the refractometer?