Use calibration fluid they said!

[907_Reefer]

Ironically I JUST posted my own thread yesterday on calibration issues with Fritz. When I first got the bottle 7 months ago, calibration was great. Stored in the dark at 62-68F, closed, no leaks, now apparently when "calibrated" to 35ppt/1.0264, it makes my RO read negative by a good margin. Currently assuming my tank has been ~.003 higher due to it, as I hadn't checked against RO in a while until last week. smh.

 

[Randy Holmes-Farley Verified Community Expert]

Ironically I JUST posted my own thread yesterday on calibration issues with Fritz. When I first got the bottle 7 months ago, calibration was great. Stored in the dark at 62-68F, closed, no leaks, now apparently when "calibrated" to 35ppt/1.0264, it makes my RO read negative by a good margin. Currently assuming my tank has been ~.003 higher due to it, as I hadn't checked against RO in a while until last week. smh.

Which refractometer?

A perfectly made brine refractometer (which is the type most often sold to hobbyists) that is perfectly calibrated to 35 ppt seawater will not read pure fresh water correctly.

 

[907_Reefer]

Which refractometer?

A perfectly made brine refractometer (which is the type most often sold to hobbyists) that is perfectly calibrated to 35 ppt seawater will not read pure fresh water correctly.

I use a VEE GEE Scientific STX-3 refractometer.

 

[Randy Holmes-Farley Verified Community Expert]

I use a VEE GEE Scientific STX-3 refractometer.

Yes, that looks like a brine refractometer, so if cannot accurately read both 0 ppt and 35 ppt seawater at the same time.

 

[Reign1]

Who is old enough where people use to use taste to check salinity. . I cannot say I ever did but did know a few and guess what there were pretty accurate when we quizzed them

 

[907_Reefer]

Yes, that looks like a brine refractometer, so if cannot accurately read both 0 ppt and 35 ppt seawater at the same time.

Checking the documentation, this refractometer does note to calibrate with distilled water. I plan to pick some up this week and report back, since initially 8 months ago (until some point in between), I was getting a reading of 0 for RO when my Fritz 35ppt was used to calibrate to 1.0264..

 

[Randy Holmes-Farley Verified Community Expert]

Checking the documentation, this refractometer does note to calibrate with distilled water. I plan to pick some up this week and report back, since initially 8 months ago (until some point in between), I was getting a reading of 0 for RO when my Fritz 35ppt was used to calibrate to 1.0264..

Yes it says to calibrate in RO/DI, but it is not intended for use in seawater, and will be inherently inaccurate to some extent if you do so.

Calibration with an accurate 35 ppt standard allows such non-seawater refractometers to be used to accurately measure seawater salinity.

The temperature of calibration is also not important, despite the claim it is, as long as you are within the ATC range. That said, there's nothing wrong with calibrating at the specified temp if you want.

 

[Randy Holmes-Farley Verified Community Expert]

For further extensive discussion of refractometers and calibration and brine refractometers, this explains it all:

Refractometers and Salinity Measurement - REEFEDITION

Title photo by R2R member Rskillz By Randy Holmes-Farley Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions Read more here...

www.reefedition.com

 

[907_Reefer]

For further extensive discussion of refractometers and calibration and brine refractometers, this explains it all:

Refractometers and Salinity Measurement - REEFEDITION

Title photo by R2R member Rskillz By Randy Holmes-Farley Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions Read more here...

www.reefedition.com

Thanks for the link! I was just looking for that article as I figured you have already answered my additional questions somewhere

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the link! I was just looking for that article as I figured you have already answered my additional questions somewhere

If not, ask away!

 

[907_Reefer]

I haven't had time to finish digesting the article yet, but in the interim I did pick up some RO and found my old RHS10ATC refractometer from our last tank, 10 years ago!

I updated my calibration thread here, essentially my old refractometer calibrated with distilled from 10 years ago (which I did at the time, still reads 1.000), shows exactly .004 higher on all levels, with the same 35ppt here reading 1.031, tank 1.028, RO & distilled 1.000. The newer refractometer calibrated with 35ppt reads ~1.027, tank at 1.024, RO/distilled -.004.

What % of tanks are off here as I see a ton calibrated with RO?!?!