Refractometer or hydrometers, shocking results

[Salty_Northerner]

I saw the BRS video where Lou Ekus mentions that a hydrometer is more precise than a refractometer since it does not require calibration. I can understand this logic so I wanted to test this theory.
So I had one glass hydrometer laying around that I used before and wanted to test this out. But the results where shocking.

Refractometer showed 35 ( 1026 ), before and after calibration.
Glass floating hydrometer showed 1020
Plastic hydrometer (no bubbles) showed something similar 1021
(everything at 25°C, so 77°F)

Ok, lets assume my I did bad calibration for the refractometer and my salinity of the refractometer is off. So how did I make sure this was not the case.
I got some corals today from a german coral farm and still had some shipping water.
Result: I also tested the corals shipping water (so an external source) and it was almost exactly in line with the results above. Although water was slightly colder.

So I'm not sure what to do now. Pretty sure refractometer is measuring 35 salinity correctly since it showed this result before and after calibration and also for the coral farm water.
But it's hard to believe that both types of hydrometers are off by almost the same value.

In all honesty my refractometer was good at the start or so I thought. Even calibration I thought it was good. Turned out I did buy the TM hydrometer and it confirmed to me that the refractometer was way out.

I purchased the Hannah salinity tester and that is what triggered everything for me and found out that the salinity was very low compared to my calibrated refractometer. So I pulled some swing arm testers out and went down to my lfs and things seemed to be close. Last night I went down to the LFS and found out that even their equipment was out of whack. The owner got one overnighted and just called me and told me that the TM was reading exactly the same as mine last night. I was literally pulling my hair out not knowing what was right and what wasn't, this tropic Marin hydrometer I put 100% faith into its accuracy.

My Hannah tester is only .01 off. TM shows 1.0255 and the Hanna shows 1.024 so now I can put the fragile one away and do a quick dip with the Hannah tester and know no that everything is chill.

 

[Salty_Northerner]

FYI: The cheap hydrometer that I used has a range of 1,000 to 1,040 (and is a lot smaller in size) while the Tropic Marin Hydrometer has a range of 1,021 to 1,031 which is way better. I guess that's the "High Precision" in the Tropic Marin product.

So I guess not every salinity hydrometer is good "enough". Still a bit shocked that both of them where off by that amount.

That's why the tropic Marin hydrometer is so big, and that's how they're able to get their accuracy in my honest opinion. 20 years ago I used to use a floating hydrometer that wasn't much larger than a pencil. And it didn't last very long as one drop and it broke lol..

This one I have right now I will only pull out to verify calibration on my hanna tester and then back in its storage container it goes so it doesn't get broken.

And to think I've been fighting this tank since January of this year all over a stupid refractometer that was misleading me from the get-go. I thought it was normal or acting normal and only needed to calibrate it once in awhile and then recently it started going all squirrely and showing my salinity was at 1.038 after calibration. So much fun in this lobby haha

 

[homer1475]

The better question would be what did you use for calibration fluid to calibrate the refractometer?

I have a TM floating hydrometer, an instant ocean floating hydrometer(plastic swing arm, thing must be 30 years old now), a milwaukee electronic refractometer, a pinpoint conductivity meter, and a hanna conductivity meter.

If I use @Randy Holmes-Farley DIY calibration fluid, I can get them all to come very close to each other(usually off by .001 to .003).

Salinity is the easiest thing in this hobby to measure, not sure why everyone has to make it so hard? Pick a device, make sure it's calibrated properly, and use only that device. Using several salinity measuring devices throws a lot of monkey wrenches into one of the easiest things in the hobby to measure.

https://reefkeeping.com/issues/2004-06/rhf/index.php

Just make sure you use the correct solution for the device your using.

 

[BeanAnimal]

The better question would be what did you use for calibration fluid to calibrate the refractometer?

I have a TM floating hydrometer, an instant ocean floating hydrometer(plastic swing arm, thing must be 30 years old now), a milwaukee electronic refractometer, a pinpoint conductivity meter, and a hanna conductivity meter.

If I use @Randy Holmes-Farley DIY calibration fluid, I can get them all to come very close to each other(usually off by .001 to .003).

Salinity is the easiest thing in this hobby to measure, not sure why everyone has to make it so hard? Pick a device, make sure it's calibrated properly, and use only that device. Using several salinity measuring devices throws a lot of monkey wrenches into one of the easiest things in the hobby to measure.

https://reefkeeping.com/issues/2004-06/rhf/index.php

Just make sure you use the correct solution for the device your using.

Get 50 people to make Randy’s DIY calibration solution and I imagine you would get to different readings from the same device.…