Tropic Marin Hydrometer vs. Hanna Salinity Checker

[DiscoStuart]

New reefer, just doing my first salinity measurements for a CUC QT tank. Started with a Hanna Salinity checker (TM hadn't arrived) and mixed water to what is showing as 34.5 ppt on a freshly calibrated unit.

Tropic Marin Hydrometer (spun to remove bubbles) is showing 1.02425 at 25.6C which equates to 32.2 PPT.
Edit: in case it matters - I just noticed I have the green version of the TM scale, which seems to the the 'ARÄOMETER' - which measures density and not SG. though from a quick search, at these temps, it should match.

Now, I know Hanna's can be off - but as this is my first time with the equipment, I'm wondering if that sounds possible/likely or there is some common human error in the mix? I assume I should mix to 35ppt based on the TM, not the Hanna, right? And as long as the Hanna is consistently off, then I'd just mix to 37 on the Hanna or whatever it comes out being?

Thanks!

.

 

[tsharpe291]

I use the tropic Marin to calibrate my refractometer , ive never used the hanna so
I can't speak of its accuracy .

 

[gbroadbridge]

New reefer, just doing my first salinity measurements for a CUC QT tank. Started with a Hanna Salinity checker (TM hadn't arrived) and mixed water to what is showing as 34.5 ppt on a freshly calibrated unit.

Tropic Marin Hydrometer (spun to remove bubbles) is showing 1.02425 at 25.6C which equates to 32.2 PPT.
Edit: in case it matters - I just noticed I have the green version of the TM scale, which seems to the the 'ARÄOMETER' - which measures density and not SG. though from a quick search, at these temps, it should match.

Now, I know Hanna's can be off - but as this is my first time with the equipment, I'm wondering if that sounds possible/likely or there is some common human error in the mix? I assume I should mix to 35ppt based on the TM, not the Hanna, right? And as long as the Hanna is consistently off, then I'd just mix to 37 on the Hanna or whatever it comes out being?

Thanks!

.

To save your sanity, just pick one instrument and use it.

Comparing devices which are measuring using different scales with different technology is a recipe for madness. They will NEVER agree.

 

[DiscoStuart]

To save your sanity, just pick one instrument and use it.

Comparing devices which are measuring using different scales with different technology is a recipe for madness. They will NEVER agree.

Totally - I'm not expecting them to match. If they are consistently off, then I can use the easy one for spot checks. That's the crux of the question. And if that hydrometer vs. Hanna gap is common (and Hanna reading that falsely high is common).

 

[DiscoStuart]

Found this old thread which has the answer. It links to an old article where the link is broken, but I found an archive of it and image is below.

The short of it is: If you are in Europe, you may end up with the GREEN target zone hydrometer. Where the US will get the BLUE one.

• Green one measures density
• Blue measures specific gravity
• Thy do not match

This calculator can convert from density to PPT or SG.

So my 1.0243 DENSITY (not SG) which I thought was a low 32.2ppt was actually 36.6 ppt. So my Hanna is reading 2.1 ppt too LOW and not too HIGH. Big difference!

 

[Stang67]

TM is the most accurate I have found. Be sure to take the water temp into consideration when doing your calculations. I use the Hanna to mix the saltwater and the TM for the overall salinity of the tank.

 

[Randy Holmes-Farley Verified Community Expert]

It is never the case that density and specific gravity match unless the temp is 4 deg C. You must convert density in a table or calculator.

 

[DiscoStuart]

Got this conversion chart from Tropic Marin support:

 

[FernBluffReef]

I have both at this point. What I can say is the Hanna is pretty accurate / stable. What isn’t accurate is their calibration solutions.

The first calibration solution I got from my LFS caused the Hanna to read about 1ppt low which is a common complaint. The next set of calibration fluid I received via online was much closer to reality. So I threw what remains of my first set out. I’m not sure if it’s improper storage or old calibration fluid as I don’t believe I found an expiration date.

Anyway. Now my Hanna reads within .2 of the TropicMarine. I only use the TropicMarine as part of water changes which provides an opportunity to check that the Hanna remains inline or if I need to recalibrate. When I need to do so I hope what calibration solution I have from the good batch remains stable.

 

[DiscoStuart]

I have both at this point. What I can say is the Hanna is pretty accurate / stable. What isn’t accurate is their calibration solutions.

The first calibration solution I got from my LFS caused the Hanna to read about 1ppt low which is a common complaint. The next set of calibration fluid I received via online was much closer to reality. So I threw what remains of my first set out. I’m not sure if it’s improper storage or old calibration fluid as I don’t believe I found an expiration date.

Anyway. Now my Hanna reads within .2 of the TropicMarine. I only use the TropicMarine as part of water changes which provides an opportunity to check that the Hanna remains inline or if I need to recalibrate. When I need to do so I hope what calibration solution I have from the good batch remains stable.

Thanks, that’s helpful. So far I just used one of the calibration solutions that came with the tester.

 

[TangerineSpeedo]

To save your sanity, just pick one instrument and use it.

Comparing devices which are measuring using different scales with different technology is a recipe for madness. They will NEVER agree.

LOL... I use the TM, Hanna, Milwaukee, Apex, and a refractometer... I also throw the saltwater against the wall like pasta to see if it sticks... (not really). Every single one has it's own use and accuracy, but will read completely different. Understanding those differences is the key...
But to be honest I use the TM for mixing SW and the Hanna for testing the tanks. I use local NSW so I can use that as a reference on my Hanna to know when it has to be calibrated again.

 

[DiscoStuart]

NSW

NSW?

 

[edsbeaker]

NSW?

Natural Saltwater.

 

[DiscoStuart]

Natural Saltwater.

Ah, of course. Thanks! I think I'll end up with a similar approach to you once I figure out the consistent difference between the TM and the Hanna. I've mixed up a couple of small batches of saltwater for a CUC QT tank and it's all just getting used to everything, but I'll get there!

 

[Otago]

Randy has an article on DIY calibration solutions here : https://www.reefkeeping.com/issues/2004-06/rhf/
The conductivity recipe is near the bottom. Tore my hair out till I started using his calibration recipes, now it all matches up as close as the specs would suggest is possible.

 

[DiscoStuart]

Randy has an article on DIY calibration solutions here : https://www.reefkeeping.com/issues/2004-06/rhf/
The conductivity recipe is near the bottom. Tore my hair out till I started using his calibration recipes, now it all matches up as close as the specs would suggest is possible.

ooh, great, much better than the cost of the hanna salinity calibration fluid! Thank you.

 

[Otago]

ooh, great, much better than the cost of the hanna salinity calibration fluid! Thank you.

You're welcome, I think they're also more accurate than the Hanna calibration packets.

 

[Reef.]

I would go by the TM…you could use the hanna for a quick check of a 10% water change etc because if its off its not going to alter the salinity that much but when you say “as long as the Hanna is consistently off” thing is you are never going to know if its consistently off or just off without constantly testing it, and for me if I have to test the tester to be sure its correct I would just use a device you know is correct every time.

 

[KStatefan]

You're welcome, I think they're also more accurate than the Hanna calibration packets.

The Hanna calibration solutions I think are the only hobby ones that are made to NIST standards. I do not calibrate mine often but it seems to hold calibration well and is consistently lower than my Tropic Marin.

 

[Otago]

The Hanna calibration solutions I think are the only hobby ones that are made to NIST standards. I do not calibrate mine often but it seems to hold calibration well and is consistently lower than my Tropic Marin.

Mine holds calibration well too ( as long as I rinse it of with RO before storage ) but before I used Randy's solution it was also always lower than my hydrometer and refractometer ( which matched ). Could be Hanna QC or user error but changing the calibration solution fixed it.