Salinity Calibration Fluid?

[Powerdrum]

I'm just curious what is best fluid to calibrate your Refractometer, also I have heard you can calibrate it just using Distilled water?? Please let me know what your thoughts are and best solution for this.
Thx!!

 

[Crabs McJones]

I'm just curious what is best fluid to calibrate your Refractometer, also I have heard you can calibrate it just using Distilled water?? Please let me know what your thoughts are and best solution for this.
Thx!!

While you can calibrate your refractometer with RO/DI water, but due to variances such as filter performance, and source water, it's not as accurate as using a known calibration.
This is what I use from BRS and it's been working great so far.
https://www.bulkreefsupply.com/aqua-craft-refractometer-calibration-fluid.html

 

[Scubabum]

I've been using Aqua Craft Refractometer calibration fluid for years. You can calibrate at Zero with Distilled water but you will get more accurate reading by calibrating with calibration fluid.

 

[Randy Holmes-Farley Verified Community Expert]

I'm just curious what is best fluid to calibrate your Refractometer, also I have heard you can calibrate it just using Distilled water?? Please let me know what your thoughts are and best solution for this.
Thx!!

A 35 ppt standard is best, if it is made correctly.

Refractometers And Salinity Measurement
http://www.reefedition.com/refractometers-salinity-measurement/

You can make your own by dissolving 3.65 weight percent sodium chloride in RO/DI water.

 

[tsav87]

Don't forget to temp match the calibration solution to your tank water temp.

 

[Randy Holmes-Farley Verified Community Expert]

Don't forget to temp match the calibration solution to your tank water temp.

If it is an ATC refractometer, that shouldn't matter, but it certainly doesn't hurt to do so.

 

[braappn]

Can a bottle of commercial calibration fluid like from BRS go bad? Can it increase in salinity from evaporation? Assuming the bottle is used like normal for a few drops and closed back up when finished.

 

[Randy Holmes-Farley Verified Community Expert]

Can a bottle of commercial calibration fluid like from BRS go bad? Can it increase in salinity from evaporation? Assuming the bottle is used like normal for a few drops and closed back up when finished.

It can "go bad" if it is allowed to evaporate (e.g., left open), but sitting in the closed bottle it should be good enough for our purposes. Open for a few minutes won't be a detectable issue.

 

[TangingOut]

I've used two commercially available calibration fluid. Pinpoint and TLF. Pinpoint I found to be garbage. Two separate bottles were different by 1 ppt.

 

[joseserrano]

It can "go bad" if it is allowed to evaporate (e.g., left open), but sitting in the closed bottle it should be good enough for our purposes. Open for a few minutes won't be a detectable issue.

would you recommend shaking the bottle before use? will results vary if you don't do this, or should solution always read fine?

 

[Randy Holmes-Farley Verified Community Expert]

would you recommend shaking the bottle before use? will results vary if you don't do this, or should solution always read fine?

If the solution is clear, shaking makes no difference. The dissolved salts do not rise or settle to the bottom. There's no reason to want any solids in the calibration, so if there are any, do not stir them up.

 

[Randy Holmes-Farley Verified Community Expert]

I've used two commercially available calibration fluid. Pinpoint and TLF. Pinpoint I found to be garbage. Two separate bottles were different by 1 ppt.

How do you know which was off, and what did you test them with? FWIW, not all fluids are suitable for all salinity measurement methods.

 

[TangingOut]

How do you know which was off, and what did you test them with? FWIW, not all fluids are suitable for all salinity measurement methods.

That's the thing, two bottles from the same company(pinpoint) should have the same reading on the same instrument. In my case a refractometer.

 

[Randy Holmes-Farley Verified Community Expert]

That's the thing, two bottles from the same company(pinpoint) should have the same reading on the same instrument. In my case a refractometer.

Sorry, I thought you meant the TLF and Pinpoint were off by 1 ppt.

 

[TheLadyCrash]

While you can calibrate your refractometer with RO/DI water, but due to variances such as filter performance, and source water, it's not as accurate as using a known calibration.
This is what I use from BRS and it's been working great so far.
https://www.bulkreefsupply.com/aqua-craft-refractometer-calibration-fluid.html

I second BRS calibration fluid. I used distilled in the past and wound up with my salinity dropping way low due to the refractometer being mis-calibrated.

 

[Sleepydoc]

There are different ways a refractometer can be inaccurate. In short, the best way to calibrate is with a fluid that is close to your desired/expected reading- a 35ppm calibration fluid is perfect for most reef tanks.

 

[bgoldb]

I have purchased 4 bottles of so called seawater refractometer calibration solutions and gave me different readings ranging from 1.025 to 1.029. 2 of the bottles were from the same company. All were tested with a MISCO refractometer as well as a Milwaukee and Red Sea Refractometer. I think it’s time to use Randy’s formula.