Refractometer Calibration Fluid Conundrum

[blkhawk10]

I've had a bottle of one BRS sells for years now and didn't seem to have an issue. My buddy was suggesting I get a new bottle and see what the reading would be, so I did. The new calibration fluid is saying the old solution is off by .005 on the lower end so the salinity in my tank I just tested reads 1.030. Does the old solution dilute with age? I would think it would evaporate making the salinity in the old solution higher than the new solution. Everything in my tank other than an anemone seems to be doing ok. Should I go with the old or new calibration?

 

[Gtinnel]

If you have some basic kitchen scales its easy to make your own calibration solution from rodi water and table salt. You can also make it by measuring the volume of the salt instead of the weight.

There are instructions in this article

https://www.reefkeeping.com/issues/2004-06/rhf/

 

[BryanM]

This is why I went to a tropic marin hydrometer.

 

[rtparty]

Don’t trust any of the pre made calibration solutions. Make your own following Randy’s recipe and go off that

 

[exnisstech]

I used Randy's recipe and it works great. Recently I started using TM hydrometer and use it to measure my fresh mixed water. I then use that water to check the calibration on my refractometers but I don't use them very often now that I have the hydrometer. My tanks don't fluctuate enough that I feel the need to test them very often so the hydrometer is my go to tool. I'd like to try a conductivity meter but haven't talked myself into spending for one yet.

 

[Randy Holmes-Farley Verified Community Expert]

I've had a bottle of one BRS sells for years now and didn't seem to have an issue. My buddy was suggesting I get a new bottle and see what the reading would be, so I did. The new calibration fluid is saying the old solution is off by .005 on the lower end so the salinity in my tank I just tested reads 1.030. Does the old solution dilute with age? I would think it would evaporate making the salinity in the old solution higher than the new solution. Everything in my tank other than an anemone seems to be doing ok. Should I go with the old or new calibration?

It does not dilute with age unless you are in an environment of 100% humidity and leave it open all the time.

Commercial hobby standards have a shoddy reputation for accuracy. They are cheap and easy to make so why someone makes inaccurate ones is quite hard to understand.

I recommend making your own. This shows how. Be sure to use the refractometer recipe:



https://www.reef2reef.com/ams/reef-aquarium-salinity-diy-calibration-standards.956/

 

[IceNein]

I have always appreciated that the coke bottle method makes so much that it's nature minimizes measuring errors. And why not? Table salt and water are so cheap.

 

[blkhawk10]

I just made the salt and water solution proposed above and the salinity was high. Thanks for the responses.

 

[Randy Holmes-Farley Verified Community Expert]

I just made the salt and water solution proposed above and the salinity was high. Thanks for the responses.

Meaning the tank salinity is high?

 

[slingfox]

I just made the salt and water solution proposed above and the salinity was high. Thanks for the responses.

The most common issue seen on this board is the cheap refractometer reads too high so the tank water is too low in salinity.

 

[blkhawk10]

Meaning the tank salinity is high?

Yes. It was up around 1.029

 

[Randy Holmes-Farley Verified Community Expert]

Ok, I understand. At least one of the two commercial standards was reasonably accurate. lol