Don't Trust Cheap Refractometers!

[aquaman3680]

Frustrating!! Purchased a cheap Amazon refractometer and Fritzs calibration solution, calibrated the refractometer and have been going off of that. I happen to pull out the old hydrometer and check using it and it was saying the SG was 1.023 much lower than the refractometer.

Now that I didn't trust what I was seeing I decided to purchase a Hanna salinity tester and the ole hydrometer was right. My "calibrated" refractometer was saying the SG was 1.027 and the Hanna salinity checker confirms the hydrometer is correct and is reading SG of 1.023.

Moral of the story, with one of the most important parameters in the tank, don't trust a cheap refractometer, go with old proven equipment or new technology with proven accuracy! Won't make that mistake again! Now to slowly raise the salinity!

 

[Sean Clark]

I agree. Don't trust or use cheap tools. My experience with the Hanna salinity checker is that it leaves a lot to be desired in the area of consistency. I have a lot of Hanna products and the salinity checker is the only one that I do not trust. Mine is all over the place. I now use a Hanna digital refractometer and calibrate it every time I use it.

 

[Savo]

I had the same issues

 

[flashsmith]

I recently lost a few corals in my frag tank because my Hanna salinity tester went crazy. Even after recalibrating it twice it was still off by 10 pts. The first packet read 1.021 so I tried another one and it read 1.026.So naturally I tried to raise my salinity with disastrous results. Now I only use an old school floating hydrometer. It's the most accurate and never needs calibration.

 

[gbroadbridge]

I recently lost a few corals in my frag tank because my Hanna salinity tester went crazy. Even after recalibrating it twice it was still off by 10 pts. The first packet read 1.021 so I tried another one and it read 1.026.So naturally I tried to raise my salinity with disastrous results. Now I only use an old school floating hydrometer. It's the most accurate and never needs calibration.

In my experience, most issues of this type are caused by not rinsing the probe in RO water and drying it before storing it.

 

[flashsmith]

In my experience, most issues of this type are caused by not rinsing the probe in RO water and drying it before storing it.

Rinse every time. I can take mine and test the same tank consecutively and get 3 different readings. Waste a couple calibration packets and it's still off. Meanwhile my TM floating hydrometer is always accurate and never needs adjusting. I use all Hanna testers but won't be buying another electronic salinity tester.

 

[ReeferLou]

My refractometer is always a few points higher than my swing arm hydrometer. So I use both now

 

[GARRIGA]

I have both the Hanna Salinity Checker along with an old school hydrometer that was used originally to verify the Hanna. Now I just calibrate the Hanna and rely on thy solely. Never used a refractometer but have considered getting a Milwaukee or Hanna that utilizes a single drop similar to the refractometer but calculates the results for me. This I would get if had my fish room again as I’m not a fan of using the same equipment from fear of spreading pathogens. The one flaw I find with the salinity checker.

 

[The1Leinad]

I have had the same issues with a cheap one, I also noticed that the slightest change in temperature really affected the readings

 

[livinlifeinBKK]

So i don't have the money for an expensive professional grade refractometer or anything similar so what should I do? Use an old school hydrometer?

 

[ggNoRe]

My calibrated cheap Amazon refractometer reading 1.0235. Got a swing arm hydrometer reading 1.028. Sent water to ATI for ICP they gave me results of 1.025. In for best option going forward...

 

[Atrumblood]

So i don't have the money for an expensive professional grade refractometer or anything similar so what should I do? Use an old school hydrometer?

If I ever doubt my salinity testing equipment I will weigh a known volume of water to get the density value. A cheap kitchen scale works for this . Get yourself a 10 - 100 mL graduated cylinder ( larger volume the better. Within reason).

Tare the weight of the clean and dry cylinder, then fill with tank water so that the level is right on the top most gradation. Weigh it and divide the weight by the volume.

It is a great fall back that is pretty bullet proof IMO.

 

[Wasabiroot]

I would even go so far as to say calibrate any salinity measuring device against a reference, no matter how accurate the tool is. Stuff drifts so you did the right thing verifying first.

 

[FishTruck]

Never trust any of them completely. Get some calibration fluid made for the job and check frequently.

 

[Atrumblood]

Never trust any of them completely. Get some calibration fluid made for the job and check frequently.

I think it should also be said to make sure your testing at 25°C. Testing the same calibration solution at anything but what it says on the bottle can easily skew your readings.

 

[HaveFishWillTravel]

Frustrating!! Purchased a cheap Amazon refractometer and Fritzs calibration solution, calibrated the refractometer and have been going off of that. I happen to pull out the old hydrometer and check using it and it was saying the SG was 1.023 much lower than the refractometer.

Now that I didn't trust what I was seeing I decided to purchase a Hanna salinity tester and the ole hydrometer was right. My "calibrated" refractometer was saying the SG was 1.027 and the Hanna salinity checker confirms the hydrometer is correct and is reading SG of 1.023.

Moral of the story, with one of the most important parameters in the tank, don't trust a cheap refractometer, go with old proven equipment or new technology with proven accuracy! Won't make that mistake again! Now to slowly raise the salinity!

I will use the Hanna when I’m making my saltwater, but I always double check it with my refractometer. I just don’t trust it completely. For one reason, it doesn’t go out as far as the refractometer in decimal points. After calibration, my Hanna seems to be pretty close so, I‘m happy with it and I trust that it is giving me a reading that is relatively close to reality. I am with a lot of you on your answers here, you have to have good tools, especially this one.

 

[Randy Holmes-Farley]

I think it should also be said to make sure your testing at 25°C. Testing the same calibration solution at anything but what it says on the bottle can easily skew your readings.

I actually never understood why some devices specify a temperature. ATC refractometers that specify to calibrate at a specific temperature seems especially odd. The ATC part, assuming it works, ensures that the reading is the same independent of temp.

The Brightwell standard above is also odd. Ignoring the obvious typo on the Brightwell bottle pictured above saying it is 53 uS/cm instead of 53 mS/cm, whatever conductivity it has is largely temperature independent since all of the conductivity devices reefers use already make corrections for temperature. 35 ppt seawater should have a conductivity of 53 mS/cm regardless of the temp used because the device should make the needed corrections.

 

[Randy Holmes-Farley]

If I ever doubt my salinity testing equipment I will weigh a known volume of water to get the density value. A cheap kitchen scale works for this . Get yourself a 10 - 100 mL graduated cylinder ( larger volume the better. Within reason).

Tare the weight of the clean and dry cylinder, then fill with tank water so that the level is right on the top most gradation. Weigh it and divide the weight by the volume.

It is a great fall back that is pretty bullet proof IMO.

Converting density to specific gravity takes some effort. How do you do it?

 

[Atrumblood]

Converting density to specific gravity takes some effort. How do you do it?

It pretty easy. It's by definition, grams / volume (mL) edit: only works for aqueous solutions.

 

[Atrumblood]

I actually never understood why some devices specify a temperature. ATC refractometers that specify to calibrate at a specific temperature seems especially odd. The ATC part, assuming it works, ensures that the reading is the same independent of temp.

The Brightwell standard above is also odd. Ignoring the obvious typo on the Brightwell bottle pictured above saying it is 53 uS/cm instead of 53 mS/cm, whatever conductivity it has is largely temperature independent since all of the conductivity devices reefers use already make corrections for temperature. 35 ppt seawater should have a conductivity of 53 mS/cm regardless of the temp used because the device should make the needed corrections.

Well I have definitely observed a behavior with my Milwaukee meter that shows the temperature correction might need some work. My meter will show a 0.001-0.002 difference if the meter itself isn't reading close to the same temperature as my tank.

I run at 25°C. Ambient is about 21-22°C. If I don't warm up the meter a bit so that the temperature reads close to 25, I get higher than usual readings. Which makes sense. Colder sea water is denser than warmer sea water. The meter doesn't seem to do a good job correcting for it.

Edit: spelling