Salinity reader which one to get?
- Thread starter Notsolostfish
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TangerineSpeedo
2500 Club Member
I used a refractometer which I thought was perfect. RODI thru 35 reference. I bought a Hanna, calibrated it and tested my water... How could my water be so far off...? It drove me nuts! I was trying to rationalize that I calibrate the refractometer with 35 reference NSW and the hanna is 35 cal is salt-water, just that, and NSW is more than just salt-water. The Hanna is basically a fancy TDS meter. So for a week I couldn’t sleep, trying to figure out what and who to trust. Then it hit me... I LIVE next to a ocean, like a few blocks away. I calibrated the hanna to their 35ppt. went to the ocean got a water sample and Bam... just like that I got my reference. I don't even calibrate my hanna anymore unless it is way off or I hit the cal button by mistake. I usually am down by the water once a week to get a piece or two of fresh kelp so I pick up a water sample while I am there. I just measure the sample with my Hanna and that will be my new weeks reference. BTW that number usually falls in between 32.5 and 33.3. so yes, if you are trying to make your water 35ppt using a hanna salinity it may be NSW high. I DO like the Hanna for the automatic temperature compensation, because I have both temperate and tropical tanks and it makes things easy.
TangerineSpeedo
2500 Club Member
No, I mean, not directly. I use the hanna 35ppt reference, to set it first. then I measure the NSW (actual ocean water) which usually ends up reading 32.5 -33.3 ppt. I use that reference point to check my tanks for the week. Which in truth is actually fairly accurate for my region. which is why I don't calibrate my hanna using local NSW, because it is not really 35ppt (local NSW). But none of that really matters, my meter can read any "X" number when I measure my local NSW as long as my tanks read the same "X" number.
monkeyCmonkeyDo
7500 Club Member
Any seawater rated ATC refractometer and calibration fluid will do. At $150 I doubt you'll not find one. Lol.
I paid $50 for my vertex one way back in the day. Had to calibrate it evertime.
My newer lfs brand one stays mostly calibrated. But I do check it everytime I use it and make.minor adjustments.
I haven't looked at prices lately for one or the cal fluid sorry. Inflation and all I could imagine they've gone up. Lol.
D
I paid $50 for my vertex one way back in the day. Had to calibrate it evertime.
My newer lfs brand one stays mostly calibrated. But I do check it everytime I use it and make.minor adjustments.
I haven't looked at prices lately for one or the cal fluid sorry. Inflation and all I could imagine they've gone up. Lol.
D
Right I think I understand now, when you test your NSW if the Hanna says it’s within 32.5-33.3 you are happy the Hanna is correct…I was just a little confused when you said this would be your reference for the week as apposed to longer.
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monkeyCmonkeyDo
7500 Club Member
monkeyCmonkeyDo
7500 Club Member
I don't trust myself to make my own calibration fluid. Lol! I can barely get the salinity right. LOLs!
D
D
Julbra
Active Member
Ah this topic is my worst nightmare. I own 3 devices just for salinity but to be honest I am not completely happy with any of them and I'm still looking for the silver bullet.
Pros:
Pros:
Pros:
Pro tips:
1. The first one is the D-D Refractometer ($40):
Pros:
- can be calibrated with very pure RODI
- extremely reliable and accurate
- precision is not fine enough for me, I can only reliably resolve within 0.3 ppt as the line can get a bit blurry
- quite tedious to use as you need a good source of light and must be meticulously cleaned after each use
2. Next I purchased is the Hanna salinity tester HI98319 ($75):
Pros:
- extremely fast temperature equalisation
- resilient to running equipment voltage
- precise and accurate within 0.1 ppt when correctly calibrated
- can be used directly in sump/tank without extracting a sample
- loses calibration rather quickly (about every week), even when correctly rinsed in RODI after each use
- calibration packets can become quite expensive if used weekly (or more in my case)
3. Finally, I also own a Lutron CD4307SD ($300) (that I also use for hydroponics):
Pros:
- can be used to measure purity of RODI as well as salinity
- extremely precise within 0.1μS/cm in the low range and 0.1mS/cm in the 35ppt range
- can be calibrated in the 35ppt range with the Hanna packets!
- keeps calibration for about 1 month if probe is maintained well
- back-lit display with separate probe makes it a very easy to use
- can be used directly in sump/tank without extracting a sample
- really (excruciatingly) slow at temperature equalisation (~3 minutes!)
- sensitive to voltage from running equipment (reading with my return pump on drops by 0.2mS/cm)
- quite expensive
- must use the Siemens unit as the built-in ppt conversion is inaccurate
Pro tips:
- most conductivity probes seem to regain their calibration to some extent when rinsed in an old calibration solution. I keep mine in a sealed container and quickly rinse the probe in it before each use (rinse with RODI before putting in tank)
- be very scared of bubbles! If any get caught in/on the probe they will dramatically lower your reading
- you need to shake the probe quite a bit in the water before to get an accurate reading
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flyingscampi
Active Member
I also use the D-D refractometer and the Hanna HI98319 and am agreement with Julbra on their pros and cons.
I don't calibrate the Hanna very often.
When I mix water (once a month) I adjust the salinity with the Hanna (so it matches the tank water.) Then I calibrate the D-D refractometer with 0 TDS RODI and test the new water. If the results of the D-D and Hanna differ by more than 0.5 ppt then (and only then) I calibrate the Hanna and restart the whole process. I probably calibrate the Hanna 2-3 times a year.
With the Hanna I always test 3 times, removing it from the water after each test. It usually settles down after the first test.
I don't calibrate the Hanna very often.
When I mix water (once a month) I adjust the salinity with the Hanna (so it matches the tank water.) Then I calibrate the D-D refractometer with 0 TDS RODI and test the new water. If the results of the D-D and Hanna differ by more than 0.5 ppt then (and only then) I calibrate the Hanna and restart the whole process. I probably calibrate the Hanna 2-3 times a year.
With the Hanna I always test 3 times, removing it from the water after each test. It usually settles down after the first test.
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BroccoliFarmer
10K Club member
Not sure I agree.
This is one of my guilty Pleasures in all of my equipment. Sets a little more than you needed to but it stays rocksteady on calibration super fast and repeatable. Don’t know what people don’t like about it.
Hanna makes great paperweights
rsumner
Active Member
Tropic Marin High Precision Hydrometer hands down. I have a closet full of manual and digital refractometers and never use them anymore. Get yourself a 500ml graduated cylinder to help test because the Tropic Marin hydrometer is long and needs float vertically in the test sample. The hydrometer is calibrated for 77 degrees. I keep my tank at 77 and always mix my salt to 77, so it's a breeze to test and never have to deal with any temperature correction. This device is simple and works 100% of the time with no possibility of variation.
ScubaScott
New Member
+1 on that. But be sure to also get a bottle of refractometer calibration solution and check/tweak the calibration each time you use it. ATC not-withstanding, the calibration can and will drift a bit.
SBSCOTTY1
New Member
the H2O refractometer, it is best to calibrate with 35ppt not rodi , I for a good while thought rodi was enough, it wasn’t.Ah this topic is my worst nightmare. I own 3 devices just for salinity but to be honest I am not completely happy with any of them and I'm still looking for the silver bullet.
1. The first one is the D-D Refractometer ($40):
Pros:
Cons:
- can be calibrated with very pure RODI
- extremely reliable and accurate
- precision is not fine enough for me, I can only reliably resolve within 0.3 ppt as the line can get a bit blurry
- quite tedious to use as you need a good source of light and must be meticulously cleaned after each use
2. Next I purchased is the Hanna salinity tester HI98319 ($75):
Pros:
Cons:
- extremely fast temperature equalisation
- resilient to running equipment voltage
- precise and accurate within 0.1 ppt when correctly calibrated
- can be used directly in sump/tank without extracting a sample
- loses calibration rather quickly (about every week), even when correctly rinsed in RODI after each use
- calibration packets can become quite expensive if used weekly (or more in my case)
3. Finally, I also own a Lutron CD4307SD ($300) (that I also use for hydroponics):
Pros:
Cons:
- can be used to measure purity of RODI as well as salinity
- extremely precise within 0.1μS/cm in the low range and 0.1mS/cm in the 35ppt range
- can be calibrated in the 35ppt range with the Hanna packets!
- keeps calibration for about 1 month if probe is maintained well
- back-lit display with separate probe makes it a very easy to use
- can be used directly in sump/tank without extracting a sample
Important! Never overreact if one device gives you a reading far from what you expected. Always double and triple check with other devices, and if they disagree, re-calibrate them and recheck before taking action. If you are going to make changes, do this very slowly (over the course of many days or even weeks if more than 1ppt) especially if you need to increase salinity.
- really (excruciatingly) slow at temperature equalisation (~3 minutes!)
- sensitive to voltage from running equipment (reading with my return pump on drops by 0.2mS/cm)
- quite expensive
- must use the Siemens unit as the built-in ppt conversion is inaccurate
Pro tips:
- most conductivity probes seem to regain their calibration to some extent when rinsed in an old calibration solution. I keep mine in a sealed container and quickly rinse the probe in it before each use (rinse with RODI before putting in tank)
- be very scared of bubbles! If any get caught in/on the probe they will dramatically lower your reading
- you need to shake the probe quite a bit in the water before to get an accurate reading
