Salinity refractometer or meter, which to believe

[Miami Reef]

@Randy Holmes-Farley

You introduced me to conductivity!

I first used hydrometers. I thought refractometers were too complicated. My salinity would be soooo off because I never calibrated the hydrometers. When using the hydrometers back to back would give wildly different results.

Then I used refractometers. They were definitely a step up, but they those blue lines were impossible to tell the difference between 1.025 and 1.026. Sometimes it would be within 3 different numbers!

As of yesterday, I have a conductivity tester by Hannah. It’s literally chef’s kiss. You dip it and it gives a digital readout. No more guesswork and it’s easy to calibrate!

With refractometers, I would need to get the PERFECT lighting and constantly focus the knob. It was a lot of unnecessary work especially because I have 6 tanks (1 DT, 5 QT’s).

Im really happy with conductivity and I wish I purchased it first. It’s easier than a hydrometer!

 

[bnord]

frankly the refractometer calibration, or meter is reasonably easy to settle as there are readily available and inexpensive standards to broker significant disagreements between approaches.

As to Mg, my old reliable Salifert is telling me consistently 1350 - and the newer (to my drawer) Red Sea is repeatedly telling me 1200.

My chalices and plates are telling me something is wrong - but not sure what it is

And my old standby Nyos nitrate kit is telling me 3 and the newly acquired Hanna HR say 13-15 - and my healthy chaeto mass and shrinking GHA remnants are telling pay attention to Nyos. No standards.

I know this is not the theme of the thread, but rely on standards, just don't confuse the issue with 2 of them. - smile

 

[ClownWrangler]

frankly the refractometer calibration, or meter is reasonably easy to settle as there are readily available and inexpensive standards to broker significant disagreements between approaches.

As to Mg, my old reliable Salifert is telling me consistently 1350 - and the newer (to my drawer) Red Sea is repeatedly telling me 1200.

My chalices and plates are telling me something is wrong - but not sure what it is

And my old standby Nyos nitrate kit is telling me 3 and the newly acquired Hanna HR say 13-15 - and my healthy chaeto mass and shrinking GHA remnants are telling pay attention to Nyos. No standards.

I know this is not the theme of the thread, but rely on standards, just don't confuse the issue with 2 of them. - smile

Though there is understandably a lot of controversy over accuracy of absolute measurements between approaches, I have concluded that when it comes to precision and repeatability, the refractometer beats the meter hands down.

In terms of precision, I can get repeatable measurements from my refractometer down to a precision of 0.0005 SG or better vs. a precision of 0.001 SG for the meter, which is horrible. Also, Meters have very poor temperature compensation, so if you take a cold sample from your basement, you can not accurately compare it to a warm sample from your aquarium without warming it up first. This is not a problem with the refractometer because the one or two drops needed stabilize to the temperature of the instrument within a minute. I suppose you could say the same about the Milwaukee instrument that uses drops, but pen type meters are useless unless measuring all samples at the same temperature.

 

[Tbg299]

Hi,
I'm new to the forum, but not new to saltwater/reef. Been away from saltwater for about 15 years.
I have 2 refractometers, a Hanna salinity meter and an old school float hydrometer. Both refractometers have been calibrated with 1.026 solution and distilled water. The meter has been calibrated with the proper cal solution.
Both refractometers are showing the salinity @ 1.027. The meter is showing 1.024 and 1.025 at times. The hydrometer shows just a hair over 1.025.

Which would you believe is correct?

I'm thinking that the 2 refractometers are correct.

Do yourself a favor and buy a Milwaukee digital refractometer

 

[Tbg299]

@Randy Holmes-Farley

You introduced me to conductivity!

I first used hydrometers. I thought refractometers were too complicated. My salinity would be soooo off because I never calibrated the hydrometers. When using the hydrometers back to back would give wildly different results.

Then I used refractometers. They were definitely a step up, but they those blue lines were impossible to tell the difference between 1.025 and 1.026. Sometimes it would be within 3 different numbers!

As of yesterday, I have a conductivity tester by Hannah. It’s literally chef’s kiss. You dip it and it gives a digital readout. No more guesswork and it’s easy to calibrate!

With refractometers, I would need to get the PERFECT lighting and constantly focus the knob. It was a lot of unnecessary work especially because I have 6 tanks (1 DT, 5 QT’s).

Im really happy with conductivity and I wish I purchased it first. It’s easier than a hydrometer!

The Hannah digital refractometer is highly innacurate from my experience.

 

[Miami Reef]

The Hannah digital refractometer is highly innacurate from my experience.

I just ripped open another calibration packet and it’s hitting 35ppt.

I need to try Randy’s recipe.

 

[Randy Holmes-Farley Verified Community Expert]

Though there is understandably a lot of controversy over accuracy of absolute measurements between approaches, I have concluded that when it comes to precision and repeatability, the refractometer beats the meter hands down.

In terms of precision, I can get repeatable measurements from my refractometer down to a precision of 0.0005 SG or better vs. a precision of 0.001 SG for the meter, which is horrible. Also, Meters have very poor temperature compensation, so if you take a cold sample from your basement, you can not accurately compare it to a warm sample from your aquarium without warming it up first. This is not a problem with the refractometer because the one or two drops needed stabilize to the temperature of the instrument within a minute. I suppose you could say the same about the Milwaukee instrument that uses drops, but pen type meters are useless unless measuring all samples at the same temperature.

You must be electing the "wrong" meter.

Good quality conductivity meters have better precision than hobby refractometers, and generally have quite good temperature compensation.

 

[Miami Reef]

You must be electing the "wrong" meter.

Good quality conductivity meters have better precision than hobby refractometers, and generally have quite good temperature compensation.

What conductivity meter do you use?

 

[Randy Holmes-Farley Verified Community Expert]

What conductivity meter do you use?

I prefer my old Orion model 128, but I've also used the Pinpoint.

The main drawback to the Pinpoint is it takes a bit longer to reach temperature equilibrium with the water to get a stable reading. The Orion did that in less than 30 seconds.

I've not used any pen type conductivity meters.

 

[Miami Reef]

I prefer my old Orion model 128, but I've also used the Pinpoint.

The main drawback to the Pinpoint is it takes a bit longer to reach temperature equilibrium with the water to get a stable reading. The Orion did that in less than 30 seconds.

I've not used any pen type conductivity meters.

Um. Which one is the Hannah salinity checker?

 

[Randy Holmes-Farley Verified Community Expert]

Um. Which one is the Hannah salinity checker?

I've never tried the Hanna conductivity meter. It's a pen type:

Marine Salinity Tester

Hanna Instruments HI98319 Marine Salinity Tester measures conductivity (EC) to determine the salinity of natural and artificial seawater within seconds.

www.hannainst.com

Salinity Range	0.0 to 70.0 ppt (g/L); 0.0 to 70.0 PSU; 1.000 to 1.041 S.G.
Salinity Resolution	0.1 ppt (g/L); 0.1 PSU; 0.001
Salinity 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.

 

[Miami Reef]

The Hannah digital refractometer is highly innacurate from my experience.

Updating back. You are correct. First, I made Randy’s solution and it came out to 37.6ppt.

I thought I measured it incorrectly.

Today I decided to measure it again. Using a digital scale for the water and the measuring spoon/cup for the Morton iodozed sea salt. It came to the same reading as yesterday’s.

My refractometer is showing 35ppt.

Thr Hannah checker is telling me my tank is 30ppt. I never even tested my tank with this before.


Do not buy that meter.

 

[arking_mark]

Tropic Marin High-Precision Hydrometer is my ground truth.

Specific Gravity vs Density Question

I have three salinity testers all calibrated with their references. Here are my tank readings: 1. Shows 1.025 kg/l, 35.5 psu, 54.1ms/cm 2. Shows 1.027 sg, 36.8 ppt 3. Shows 1.028 sg Water temp is 77 Per this calculator: https://www.hamzasreef.com/Contents/Calculators/WaterDensity.php 1.025...

www.reef2reef.com

 

[Miami Reef]

Tropic Marin High-Precision Hydrometer is my ground truth.

Specific Gravity vs Density Question

I have three salinity testers all calibrated with their references. Here are my tank readings: 1. Shows 1.025 kg/l, 35.5 psu, 54.1ms/cm 2. Shows 1.027 sg, 36.8 ppt 3. Shows 1.028 sg Water temp is 77 Per this calculator: https://www.hamzasreef.com/Contents/Calculators/WaterDensity.php 1.025...

www.reef2reef.com

Thank you. I never knew this was an option. Sounds like my golden ticket! Thank you very much for bringing this to my attention!

 

[Tbg299]

Thank you. I never knew this was an option. Sounds like my golden ticket! Thank you very much for bringing this to my attention!

The Milwaukee digital refractometer is the best IMO. I have two mechanical refractomers which I painstakingly adjust for temperature calibration, and the Milwaukee is always spot on. It also accounts for temperature variations in S.G. which is extremely useful.

 

[Randy Holmes-Farley Verified Community Expert]

The Milwaukee digital refractometer is the best IMO. I have two mechanical refractomers which I painstakingly adjust for temperature calibration, and the Milwaukee is always spot on. It also accounts for temperature variations in S.G. which is extremely useful.

Just a clarification...

It doesn't measure specific gravity, and I do not think it makes the minor corrections in sg as a function of temperature (those are actually quite small unless the temperature changes a lot)

What it (and many refractometers) correct for is the change in refractive index with temperature, which is uses to determine specific gravity.