What to do about conflicting salinity readings?

[piscivorous]

So I have a good quality reef refractometer and checked my water this morning...1.026. I take it up to my LFS which I trust and they are very knowledgeable...they just calibrated their refractometer this morning...and they are getting 1.023. I double checked my refractometer calibration and it was spot on. I looked through theirs to double check, and sure enough it was 1.023. So obviously there is some variation between the two refractometers. Which is right? .003 swing can be a big difference it seems to some fish and corals. I'd like to figure this out. What should I do?

 

[Michael]

id suggest you stick to your refractometer and keep it calibrated, even if its 1.023 and not 1.026 true reading (imo a little low) at least its stable, thats vital.

 

[returnofsid]

What fluid are you using to calibrate your refractometer? Most people use RO/DI water, including myself. But for some refractometers, this isn't an accurate way to calibrate. Is it an ATC refractometer? (Automatic Temperature Correcting)

 

[piscivorous]

I have the Sybon salinity refractometer from Premium Aquatics. I am using the fluid that it came with to calibrate it, which reads 0. Though I am seeing now on the premium aquatics website that new evidence suggests caibrating it with some kind of salinity fluid. When calibrated with the salinity fluid and then going back to RO/DI water it should have a slight negative reading. If that is the case, then I wonder if 1.023 is actually what it is? Maybe I should try picking up some of this salinity fluid for calibrating....

 

[returnofsid]

If your calibration fluid is old, some liquid could have evaporated, causing a false high reading. There are ways to make your own calibration fluid. Unfortunately, with the search function not working, I can't find the threads. Check out the chemistry forum though, and you'll probably find something. Or try a couple Google searches.