Salinity - What to Trust?

[shanedag]

I've assumed I've been okay for the past few months, but now I've lost trust in my salinity tests. Since standing up my tank, I've been using both the Milwaukee MA887 Seawater Refractometer AND the Neptune salinity probe.

For the Milwaukee Refractometer, I use the Naslow Distilled Water to calibrate. I've then validated using the Naslow 1.025SG solution. After, my tank water has always been steady at 35ppt. Recently, I tested with the Milwaukee using the 35PPT Refractometer Calibration Solution from Aqua Craft and I consistently get a reading of 37PPT. I am not clear why this is off, but the 1.025SG solution from Naslow reads correctly.

For my Apex, I've calibrated multiple times using the 53,000 Reference Solution. I've been steady with a 35.5 - 35.7PPT reading. A bit higher than what my Milwaukee has read, but I've chalked this up to just minor differences and haven't worried too much.

Most recently, I acquired the Hanna Salinity tester. I calibrated using the included 35PPT solution and I get a 33.2-33.3PPT reading on my saltwater every time.

I'm lost on which one to trust. Given that my Milwaukee is reading 2PPT lower than the calibration solution (which matches the differences in my Milwaukee and Hanna), I'm inclined to say I need to slowly increase my salinity by 2PPT. I have corals and fish in there and they all look happy so I'm reluctant to change things but I also want to maintain 35PPT water.

Any thoughts on what I may be doing wrong and/or advice on how to proceed?

 

[Snoopy 67]

Salinity probes are not that reliable.
Given that your Milwaukee is the one you trusted & the tank is fine I would stick with it.
We get ourselves in trouble when there are too many things doing the same thing.

 

[Daniel92481]

FWIW, my Hanna has always been on point.

 

[Soryu]

Milwaukee Accuracy: ±2 PSU | ±2 ppt | ±0.002 S.G. (20/20) |
Hanna Accuracy: ±1 ppt for 0.0 to 40.0 ppt; ±2 ppt for readings over 40.0 ppt; ±1 PSU for 0.0 to 40.0 PSU ; ±2 PSU for readings over 40.0 PSU; ±0.001 S.G.

Generally speaking, I find my Hanna to be spot on most of the time, I've seen videos where the Hanna tester against known solutions seems to nail the accuracy as stated on the device. I have not invested in the Milwaukee due to the range of accuracy vs the Hanna.

 

[Davem24]

Hydrometer. Nothing to go wrong.

 

[King Turkey]

Milwaukee for me it does the trick simple to calibrate simple to use.

 

[aquakj]

Hey I would just go with the mindset that your refractometer will be off by +1 or -1 and just adjust whenever you need to. The important thing is to keep the salinity consistent and not let it change from 1.026 to 1.022 from one day to another. Also Ive seen a lot of people use the instant ocean hydrometer to compare against the fancier salinity testers and in my experience the IO hydrometer is always pretty accurate. so maybe trying comparing it to that

 

[cmaxwell39]

My hannah seemed to be off of the Salinity probe on my GHLby a 2-3 PPT until I made sure to float the calibration solution for each in the sump to make sure they were both up to the same temp when calibrating. Then they both read within a couple of tenths of a PPT of each other. And seem to track with each other consistently.

Temperature can play a vital role in calibrating these iinstruments, even when they have ATC.

 

[Randy Holmes-Farley]

I've assumed I've been okay for the past few months, but now I've lost trust in my salinity tests. Since standing up my tank, I've been using both the Milwaukee MA887 Seawater Refractometer AND the Neptune salinity probe.

For the Milwaukee Refractometer, I use the Naslow Distilled Water to calibrate. I've then validated using the Naslow 1.025SG solution. After, my tank water has always been steady at 35ppt. Recently, I tested with the Milwaukee using the 35PPT Refractometer Calibration Solution from Aqua Craft and I consistently get a reading of 37PPT. I am not clear why this is off, but the 1.025SG solution from Naslow reads correctly.

For my Apex, I've calibrated multiple times using the 53,000 Reference Solution. I've been steady with a 35.5 - 35.7PPT reading. A bit higher than what my Milwaukee has read, but I've chalked this up to just minor differences and haven't worried too much.

Most recently, I acquired the Hanna Salinity tester. I calibrated using the included 35PPT solution and I get a 33.2-33.3PPT reading on my saltwater every time.

I'm lost on which one to trust. Given that my Milwaukee is reading 2PPT lower than the calibration solution (which matches the differences in my Milwaukee and Hanna), I'm inclined to say I need to slowly increase my salinity by 2PPT. I have corals and fish in there and they all look happy so I'm reluctant to change things but I also want to maintain 35PPT water.

Any thoughts on what I may be doing wrong and/or advice on how to proceed?

The APEX 53,000 uS/cm and the Hanna 35 ppt solutions should be identical.

Cross check them and see. That might be all or part of the problem if one of them is off.

 

[shanedag]

The APEX 53,000 uS/cm and the Hanna 35 ppt solutions should be identical.

Cross check them and see. That might be all or part of the problem if one of them is off.

Thanks! That's really helpful to know. Interestingly, I just measured the Apex 53,000 solution AND the Hanna solution with my Hanna tester. Hanna tester read 35 on the Hanna solution and 33.2 on the Apex solution. The 33.2 is exactly what my tank water is measuring with the Hanna tester. I think this means my tank water is okay and the Hanna tester is off?

 

[shanedag]

Thanks! That's really helpful to know. Interestingly, I just measured the Apex 53,000 solution AND the Hanna solution with my Hanna tester. Hanna tester read 35 on the Hanna solution and 33.2 on the Apex solution. The 33.2 is exactly what my tank water is measuring with the Hanna tester. I think this means my tank water is okay and the Hanna tester is off?

Or maybe the Hanna solution is off

 

[ShepherdReefer]

I kinda use three different testers and take the average. Currently, those are Milwaukee MA887, the refractometer, and the Apex probe. I'm not saying this is the answer but what has been working for me.

 

[Cory]

You need to make your own standard. Ive never trusted the ones from stores and proven to myself the one i had was wrong. Randy has a diy standard somewhere.

 

[Reef.]

You need to make your own standard. Ive never trusted the ones from stores and proven to myself the one i had was wrong. Randy has a diy standard somewhere.

Buy a tropic Marin hydrometer.

Here is Randy’s DIY solution

You need 0.01g scales, $20 from amazon

3.65g of table salt mixed with 96.35g of rodi water.

 

[Cory]

Buy a tropic Marin hydrometer.

Here is Randy’s DIY solution

You need 0.01g scales, $20 from amazon

3.65g of table salt mixed with 96.35g of rodi water.

I have 2 swing arm hydrometers, a tropic marine floating hydrometer, a sybon refractometer, and a milwalkee digital refractometer. All read nearly the same except the swing arms. My next goal is a conductivity meter lol.

 

[vetteguy53081]

Thanks! That's really helpful to know. Interestingly, I just measured the Apex 53,000 solution AND the Hanna solution with my Hanna tester. Hanna tester read 35 on the Hanna solution and 33.2 on the Apex solution. The 33.2 is exactly what my tank water is measuring with the Hanna tester. I think this means my tank water is okay and the Hanna tester is off?

Calibrate Hanna
Had the same issue and calibration corrected it. There’s a you tube video on the procedure

 

[Reef.]

I have 2 swing arm hydrometers, a tropic marine floating hydrometer, a sybon refractometer, and a milwalkee digital refractometer. All read nearly the same except the swing arms. My next goal is a conductivity meter lol.

The only issue I find with the hydrometers is the temp charts tend to be slightly off, not much but I’ve tested it a couple of times now, took a reading when cold and looked up the actual salinity on the chart, then heated the water to 25c and get a different reading, the chart is slightly off most of the time.

I now just heat the water to 25c so I don’t have to use the temp charts.

 

[Randy Holmes-Farley]

With two standards that differ, there's no way to tell which is correct without further tests, such as a third one.

 

[Hincapiej4]

High Precision Hydrometer

Ensure that your equipment is reading correctly and your aquarium is at the right salinity with Tropic Marin's High Precision Hydrometer. Many tank inhabitants are sensitive even to minor changes of the water conditions. Unfortunately as we've all experienced, salinity reading equipment as...

www.bulkreefsupply.com

 

[Tuffloud1]

Buy a tropic Marin hydrometer.

Here is Randy’s DIY solution

You need 0.01g scales, $20 from amazon

3.65g of table salt mixed with 96.35g of rodi water.

Is this for 1.026, 35 ppt? Can this solution be used in a refractometer? @Randy Holmes-Farley

I mixed this solution the best I could. My scale can read 0.1 but not .01.