Reading Salinity

[Reefer1978]

I seem to be spending a ton of my time lately trying to get salinity right, and can't seem to align between all my testers. I have the following to check with:
1. Vertex Refractometer
2. eBay Refractometer
3. Milwaukee MA887
4. Instant Ocean Hydrometer
and I am using AccuraSea salinity reference solution on 1 - 3.

1. Vertex: One of the older, but build wise best refractometer I have ever used. Calibrated to 1.026, tank water reads 1.020

2. eBay: Calibrated to 1.026, tank water reads 1.023

3. Milwaukee MA887: with reference solution reads 1.026 (or 1.027 if multiple tests are performed, I am assuming due to temp calibration). Tank water reads 1.022.

4. Instant Ocean Hydrometer: I am honestly tired of using hydrometer, as air bubbles keep messing with the reading and I can't seem to get all bubbles out from the needle.

So which one do I trust?

 

[geologeek]

Definitely not No. 4!

How old are your calibration solutions?

Although the refractometers have auto temp calibration, have you tried warming your calibration solution to tank temp and calibrate then? Also what do you get on each with RODI water?

As it stands, I would think the Milwaukee is the most accurate......but that depends on your calibration.

Why not add to your list a floating hydrometer...... probably the most accurate and cheapest addition.

But something is wrong with either your calibration fluids, your technique or some of your equipment needs to be recycled......

 

[Gumbies R Us]

The BRS High Precision Hydrometer is one that many people use and say is accurate!

 

[Mr. Mojo Rising]

I would get a hanna digital tester and I trust that (sorry I guess I'm no help)

 

[Reefer1978]

Definitely not No. 4!

How old are your calibration solutions?

Although the refractometers have auto temp calibration, have you tried warming your calibration solution to tank temp and calibrate then? Also what do you get on each with RODI water?

As it stands, I would think the Milwaukee is the most accurate......but that depends on your calibration.

Why not add to your list a floating hydrometer...... probably the most accurate and cheapest addition.

But something is wrong with either your calibration fluids, your technique or some of your equipment needs to be recycled......

Calibration solution is fresh. For RO, Milwaukee reads 0. Refractometers dwarf higher as they are calibrated with 1.026, and of course if I calibrate with 0, they read salinity lower.

The BRS High Precision Hydrometer is one that many people use and say is accurate!

Agree, but do I really need more equipment for such a silly thing?

I would get a hanna digital tester and I trust that (sorry I guess I'm no help)

Confirmed, you are of no help! Just kidding Mojo, thanks for jumping into the thread.

 

[Randy Holmes-Farley Verified Community Expert]

I would make my own calibration solution for any and all devices I used to check them:

https://www.reef2reef.com/ams/reef-aquarium-salinity-diy-calibration-standards.956/

 

[Reefer1978]

I would make my own calibration solution for any and all devices I used to check them:

https://www.reef2reef.com/ams/reef-aquarium-salinity-diy-calibration-standards.956/

Hi Randy, any reason to doubt the reference solution I already have?

 

[Randy Holmes-Farley Verified Community Expert]

Hi Randy, any reason to doubt the reference solution I already have?

What brand? Some folks find commercial solutions not accurate. Like anything, some brands may be more reliable than others.

You also can make enough to test larger devices such as hydrometers.

 

[Reefer1978]

What brand? Some folks find commercial solutions not accurate. Like anything, some brands may be more reliable than others.

You also can make enough to test larger devices such as hydrometers.

I am using AccuraSea. My bigger concern, why am I getting different readings with so many test methods?

 

[Randy Holmes-Farley Verified Community Expert]

I am using AccuraSea. My bigger concern, why am I getting different readings with so many test methods?

Which is why testing them all against an appropriate standard will answer your question.

I would not just assume your current one is accurate.

 

[hoffmeyerz]

You will def find several different views on this topic as everyone has their own method that they trust.
My .02 is consistency is what's most important so pick one and always use that one with the same testing method Everytime. I ofcourse agree with Randy to make your own calibration solution, again for consistency.
Pick your favorite tester and run with it. Personally I decided to use the Tropic Marine floating hydrometer as it never needs to be calibrated and as long as temp is correct will always read right.

 

[Reefer1978]

Which is why testing them all against an appropriate standard will answer your question.

I would not just assume your current one is accurate.

I will make my own reference solution in a bit (this afternoon). Assuming I do, and calibrate all 3 with the same, and still get 3 different readings from the tank, that's the next step?

 

[FishTruck]

I personally prefer a refractometer for weekly checks, and I use a conductivity probe for constant measurement.

I only expect them to agree at 35 ppt tank water (for my sanity).

Note: I use two different calibrations fluids, one for refractometers and one for conductivity probes. If they can't be made to agree that way..., I make sure the refractometer is correct - and then make my own calibration fluid out of tank water for the conductivity probe and "force it" to agree with the the conductivity probe at tank water 35 ppt. I'm only looking for stability after all, not actual scientific precision.

Here is an idea. SInce your refractometers don't agree - do this. Take your 1.026 calibration (where they do agree) and dilute it down to make it 1.020 - by chemisty. See which one reads correctly and the other one goes in the trash.

 

[Reefer1978]

I personally prefer a refractometer for weekly checks, and I use a conductivity probe for constant measurement.

I only expect them to agree at 35 ppt tank water (for my sanity).

Note: I use two different calibrations fluids, one for refractometers and one for conductivity probes. If they can't be made to agree that way..., I make sure the refractometer is correct - and then make my own calibration fluid out of tank water for the conductivity probe and "force it" to agree with the the conductivity probe at tank water 35 ppt. I'm only looking for stability after all, not actual scientific precision.

Here is an idea. SInce your refractometers don't agree - do this. Take your 1.026 calibration (where they do agree) and dilute it down to make it 1.020 - by chemisty. See which one reads correctly and the other one goes in the trash.

Thank you for the idea, I will try it for sure. I already know Vertex is more accurate tho.

 

[djkms]

I have gone round and round with different salinity testers and various reference solutions. Start with Randy's recipe with table salt. Why - because you can reproduce it with the same results until the cows come home. its consistent and you are in control of the consistency. All these various reference solutions are not reliable. How do you know they are consistent from batch to batch? You don't, just trust them? No thanks.

Now as far as testing - I use the Hanna Salinity checker. Why? Because it reads to the 10th of a point (not aware of any other tester that does this) and I can calibrate it with Randy's solution which I do once a month. My salinity results from ICP test to ICP are consistent with this method as well.

 

[Randy Holmes-Farley Verified Community Expert]

Thank you for the idea, I will try it for sure. I already know Vertex is more accurate tho.

Well, the first thing is you cannot use the same diy solution for all of them. Hydrometer needs a different solution.

Second point is the first two refractometers will be calibrated using it so necessarily will read it correctly. Do not calibrate them any other way.

The Milwaukee cannot do that, but calibrate it with ro/di them measure the standard.

 

[exnisstech]

Pick one and roll with it. Using 4 testers is just going to cause problems. I mean if you want to drive yourself crazy trying to get all 4 to match have at it but it wouldn't be my idea of a good time.
I use a refractometer calibrated with Randy's calibration fluid. I keep a TM hydrometer just incase I get an unusual reading on the refractometer but that hasn't happened yet.

 

[FernBluffReef]

Definitely not No. 4!

How old are your calibration solutions?

Although the refractometers have auto temp calibration, have you tried warming your calibration solution to tank temp and calibrate then? Also what do you get on each with RODI water?

As it stands, I would think the Milwaukee is the most accurate......but that depends on your calibration.

Why not add to your list a floating hydrometer...... probably the most accurate and cheapest addition.

But something is wrong with either your calibration fluids, your technique or some of your equipment needs to be recycled......

lol # 4 is my preferred. My refractor meter is useless. I got a Hanna salinity checker for quick checks. It tends to read a bit low but isn’t bad. Last time I calibrated the salinity checker it matched my Instant Ocean so it’s not going to be recalibrated until the two disagree. The refractor meter always disagrees save if calibrated every test - useless - maybe it’s my eyes

 

[schooncw]

I don't get all of the hand-wringing, uncertainty and expense people go through, when this simple tool is virtually flawless, requires no maintenance and has a maximum deviation of about 0.001 at 77 degrees F.

 

[Reefer1978]

I don't get all of the hand-wringing, uncertainty and expense people go through, when this simple tool is virtually flawless, requires no maintenance and has a maximum deviation of about 0.001 at 77 degrees F.

But it aint digital!!! Jokes aside, yes valid point, but personally I had these tools already.