Salinity Confusion. Is there a definitive way to calculate this?

DeputyDog95

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Here are the nuts and bolts. Sorry for the long post.

I was using the Milwaukee digital refractometer for a while, but I found it could be wonky and seemed to read high as compared to LFS tanks and posts I've read online where other people found it to read high as well.

It was suggested that I get the Hanna conductivity meter, which I did around 4 months ago.

Quite honestly, I have been thrilled with it. Easy to calibrate, easy to read. It has been very consistent and seemed to be accurate as it rarely drifted from the 35ppt calibration standard.

Recently, I thought I should have a backup to "check my checker", so I bought the BRS LED backlit refractometer that came with BRS calibration fluid.

So here's what I did to make sure I had an apples to apples comparison.

Calibrated the Hanna to 35ppt using the supplied Hanna solution. I then tested the Hanna solution which tested right at 35ppt.

I then tested the tank water using the Hanna checker and it came in at 35.1 ppt, as I expected it to based on previous readings.

Next I calibrated the BRS refrac to 35ppt using their solution and tested my tank water as well as two more reference standards (Marine Fauna and Algoid) which are supposed to be 35ppt.

I also happened to get some corals in today from Jason Fox, so I thought why not test his water too and see what happens?

Here is how the measurements went with the BRS refrac calibrated to the 35ppt BRS solution:

My tank water: 40ppt
Marine Fauna: 40ppt
Algoid: 40ppt
Jason Fox's water: 31ish ppt

Here is how the measurements went with the Milwaukee digital refrac calibrated which had been calibrated using distilled water:

My tank water: 36ppt
BRS: 34ppt
Marine Fauna: 36ppt
Algoid: 37ppt
Jason Fox's water: threw his water out before I thought to test it

The Hanna is a conductivity meter probe so I couldn't test the other reference solutions and now I'm forgetting what the Hanna said Jason Fox's water was. Grrrr. It was much lower than I expected it to be, but I should have wrote it down.

My recent ICP tests which don't actually read salinity but calculate it somehow come in at 34.9ppt.

So now I'm totally confused and am not sure what to believe.

Any thoughts on this? I wish I could have a definitive way of measuring this, once and for all.
 

Pntbll687

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Here are the nuts and bolts. Sorry for the long post.

I was using the Milwaukee digital refractometer for a while, but I found it could be wonky and seemed to read high as compared to LFS tanks and posts I've read online where other people found it to read high as well.

It was suggested that I get the Hanna conductivity meter, which I did around 4 months ago.

Quite honestly, I have been thrilled with it. Easy to calibrate, easy to read. It has been very consistent and seemed to be accurate as it rarely drifted from the 35ppt calibration standard.

Recently, I thought I should have a backup to "check my checker", so I bought the BRS LED backlit refractometer that came with BRS calibration fluid.

So here's what I did to make sure I had an apples to apples comparison.

Calibrated the Hanna to 35ppt using the supplied Hanna solution. I then tested the Hanna solution which tested right at 35ppt.

I then tested the tank water using the Hanna checker and it came in at 35.1 ppt, as I expected it to based on previous readings.

Next I calibrated the BRS refrac to 35ppt using their solution and tested my tank water as well as two more reference standards (Marine Fauna and Algoid) which are supposed to be 35ppt.

I also happened to get some corals in today from Jason Fox, so I thought why not test his water too and see what happens?

Here is how the measurements went with the BRS refrac calibrated to the 35ppt BRS solution:

My tank water: 40ppt
Marine Fauna: 40ppt
Algoid: 40ppt
Jason Fox's water: 31ish ppt

Here is how the measurements went with the Milwaukee digital refrac calibrated which had been calibrated using distilled water:

My tank water: 36ppt
BRS: 34ppt
Marine Fauna: 36ppt
Algoid: 37ppt
Jason Fox's water: threw his water out before I thought to test it

The Hanna is a conductivity meter probe so I couldn't test the other reference solutions and now I'm forgetting what the Hanna said Jason Fox's water was. Grrrr. It was much lower than I expected it to be, but I should have wrote it down.

My recent ICP tests which don't actually read salinity but calculate it somehow come in at 34.9ppt.

So now I'm totally confused and am not sure what to believe.

Any thoughts on this? I wish I could have a definitive way of measuring this, once and for all.
Sounds like allot of testing for salinity. Seems like the brs refract may be off, but I don't know.

I'm a huge fan of the Tropic Marin glass hydrometer, no calibration needed and accurate to .001 on readings. Measure salinity at 1.025 means the salinity is somewhere between 1.024-.026. Measure twice and be done.

I'm not a fan of refractometers you have to hold up to your eye, I have glasses and have a hard time reading the graphs.
 

EeyoreIsMySpiritAnimal

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I'm a huge fan of the Tropic Marin glass hydrometer, no calibration needed and accurate to .001 on readings. Measure salinity at 1.025 means the salinity is somewhere between 1.024-.026. Measure twice and be done.
^^ THIS 100%!!
Just be sure to calculate for temps over/under 77F.
 

Pntbll687

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^^ THIS 100%!!
Just be sure to calculate for temps over/under 77F.
I keep my reef at 77-78, so no calculations needed!

I really don't know why people seem to put down the glass hydrometer. I think it has to do with it just providing a reading in a simple way, and not being a digital readout or the user having to do something like looking through a refractometer.
 

Pntbll687

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Temp calculations are not necessary if the refractometer has ATC (automatic temperature compensation). Just need to wait 20 seconds before taking the reading.
he was talking about using the glass hydrometer
 

EeyoreIsMySpiritAnimal

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he was talking about using the glass hydrometer
She. And yes, I was referring to the lab calibrated glass floating hydrometer.
 

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