S.G. mystery

[zbrusko]

Hi,

I have a minor salinity/S.G. mystery. For context, my tank is at 78F, and my room is 65F at time of testing. Using a Milwaukee MA887 refractometer:
My tank reads 1.027
The included standard solution reads as 1.028
Two Little Fishies AccurasSea reads as 1.028

Both standards are listed as 1.025. So to me, this means my refractometer is off by .003 S.G, therefore my tank is 1.024. I’ve seen others report the same issue, but I wanted to confirm this, so I ordered the Tropic Marin Hydrometer. When I use this to test my tank, I get 1.0267, which is in line with the refractometer. I am assuming this is the most accurate. Is it possible both of my test solutions are that wrong, and my refractometer is actually quite spot on? Do these values even matter so long as I am consistant?

Thanks for any input.

 

[edsbeaker]

Yes, it’s possible that the solutions can be that off. I would trust that the TM hydrometer is correct. I, personally, haven’t heard of any cases that a TM hydrometer was reading incorrectly, but I guess it’s possible. The hydrometer will also be consistent without ever needing calibration. The only thing is that the hydrometer is dependent on temperature. I use the link below for adjustments if water temp is not 77 degrees.

https://www.hamzasreef.com/Contents/Calculators/SalinityCorrection.php

 

[X-37B]

The TM hydrometer is all I use.
The difference in a SG of 1.026 at 77°f to 80°f is only off by 0.0005 for a reading of 1.0265 at 80°f.
That's small enough not to matter, imo, to me anyway.
The main thing is to just keep the number the same day to day.
I run 1.026-1.027 with 1.0265 as my target.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, the Milwaukee only claims accuracy of +/- 0.002 in specific gravity, so a true 1.026 could read anywhere from 1.024 to 1.028 and still be within perfect specification.

When you say the "included standard solution", what is that? Who makes it and what exactly does it say?

 

[zbrusko]

FWIW, the Milwaukee only claims accuracy of +/- 0.002 in specific gravity, so a true 1.026 could read anywhere from 1.024 to 1.028 and still be within perfect specification.

When you say the "included standard solution", what is that? Who makes it and what exactly does it say?

Here is the bottle.

 

[Randy Holmes-Farley Verified Community Expert]

I believe I’ve seen that one before associated with issues, so I would not trust it.

 

[zbrusko]

I believe I’ve seen that one before associated with issues, so I would not trust it.

Thanks. So it seems my refractometer may be pretty accurate, and that anything in the 1.025-1.027 range should be good as long as I keep it consistent? Is that fair to say?

 

[Randy Holmes-Farley Verified Community Expert]

Thanks. So it seems my refractometer may be pretty accurate, and that anything in the 1.025-1.027 range should be good as long as I keep it consistent? Is that fair to say?

Yes. :)

 

[zbrusko]

Yes. :)

Thanks!