Calibrating refractometer

[.AcroKiller.]

I been using the Aqua craft solution but I don't know if I should trust it.
I tested the aqua craft solution on a digital refractometer and the reading came out to 37ppt

I regularly use an ATC refractometer with the aqua craft solution.

Today I decided to follow your article and calibrate my ATC refractometer with RO/DI water and the tested the solution and it read 36ppt same as my water in the aquarium. So as your article describe there could be an error of +/- 1ppt

Should I lower my salinity to 35ppt?

Or should I try a different solution like accurasea ?

 

[Randy Holmes-Farley Verified Community Expert]

I don't know much about the Aquacraft solution. I suspect many of the commercial solutions available now follow my recipe, but I do not know if they did, or if they did it correctly.

When you say digital, was it the Milwaukee MA887?

FWIW, calibrating with RO/DI on a brine refractometer may have random manufacturing errors, but if made perfectly, it would not be +/- 1 ppt from the RO/DI, but would necessarily read ~ 1.7 ppt too high.

So I'm not sure that there is a problem. Or if so, in what direction.

Fortunately, there's quite a bit of leeway in the salinity that works well, so it may not matter.

 

[.AcroKiller.]

Yes it was the MA887 I only used it to test the solution.

 

[.AcroKiller.]

 

[.AcroKiller.]

 

[Randy Holmes-Farley Verified Community Expert]

It says the right things, but, of course, I can't be sure it was made right or hasn't evaporated (which would lead to higher readings).

 

[.AcroKiller.]

Here is the refractometer I use. I got it from BRS

 

[.AcroKiller.]

It says the right things, but, of course, I can't be sure it was made right or hasn't evaporated (which would lead to higher readings).

What do you think about the accurasea. TLF claims they use natural sea water with their solution

 

[Randy Holmes-Farley Verified Community Expert]

There's no benefit to using one made from natural seawater as opposed to NaCl (except that the exact same solution can be used for conductivity, refractometers and hydrometers) , but I trust that Two Little Fishies has it made to the correct refractive index and expect it is a fine way to go.