Red Sea refractometer VS Amazon ATC refractometer

Ryan Rioux · Oct 3, 2016

Has anyone had experience with either of these products? I've recently used both. The Amazon ATC refractometer broke on me after the 2nd use , so I had to buy a Red Sea at a local store . 3x the money of the ATC. When I was measuring salinity with the ATC of my tank I was getting 1.023-1.024. When I am measuring with the Red Sea , I am getting the line that is 1.021-1.022. Both are required to be calibrated with Distilled or R/O water . Wondering if anyone has ever experienced 2 refractometers measuring different readings

cromag27 · Oct 3, 2016

Neither are required to be calibrated with rodi. in fact, that does more harm than good. use calibration solution. also, atc isn't a brand or model name. it stands for 'auto temp compensation'. a lot of refractometers are atc.

Ryan Rioux · Oct 4, 2016

cromag08 said:
Neither are required to be calibrated with rodi. in fact, that does more harm than good. use calibration solution. also, atc isn't a brand or model name. it stands for 'auto temp compensation'. a lot of refractometers are atc.

I dislike the Red Sea refractometer a lot. Where can I find the calibration fluid.

cromag27 · Oct 4, 2016

Check with bulk reef supply, marine depot or Milwaukee instruments.

Ryan Rioux said:
I dislike the Red Sea refractometer a lot. Where can I find the calibration fluid.

cromag27 · Oct 4, 2016

Check with bulk reef supply, marine depot or Milwaukee instruments.

Ryan Rioux said:
I dislike the Red Sea refractometer a lot. Where can I find the calibration fluid.

Ryan Rioux · Oct 4, 2016

cromag08 said:
Check with bulk reef supply, marine depot or Milwaukee instruments.

Thank you! I'll find it.

dragon99 · Oct 4, 2016

Definitely calibrate with 35ppt fluid instead of RODI. One (or both) refractometers may have a slope mis-calibration which is causing the readings to be different at your salinity even when they read the same at 0.

Ryan Rioux · Oct 4, 2016

dragon99 said:
Definitely calibrate with 35ppt fluid instead of RODI. One (or both) refractometers may have a slope mis-calibration which is causing the readings to be different at your salinity even when they read the same at 0.

I read somewhere though that the Red Sea refractometer has to be recalibrate do every single time you use it. That's a pain.

cromag27 · Oct 4, 2016

That is best practice for all refractometers, even the digital ones.

Ryan Rioux said:
I read somewhere though that the Red Sea refractometer has to be recalibrate do every single time you use it. That's a pain.

Ryan Rioux · Oct 4, 2016

cromag08 said:
That is best practice for all refractometers, even the digital ones.

I don't understand why the directions say to use distilled water to calibrate them. That's what I had been doing the whole time

cromag27 · Oct 4, 2016

Where do you see that?

Ryan Rioux said:
I don't understand why the directions say to use distilled water to calibrate them. That's what I had been doing the whole time

Ryan Rioux · Oct 4, 2016

cromag08 said:
Where do you see that?

On the directions to the original refractometer I had been using , and also on the Red Sea directions . Both state to use distilled or RO water . If they had stated to use the fluid I would have from the beginning.

madweazl · Oct 4, 2016

For giggles I tested my old Coralife Deep Six against my refractometer and they're dead on at 1.0255 (well, best I can make out on the refractometer anyways) @ 78.8°.

AdamNC · Oct 4, 2016

The Red Sea states in the manual to use RO/DI for calibration. I doubt they would have stated that if it's not how you calibrate it.

madweazl · Oct 4, 2016

AdamNC said:
The Red Sea states in the manual to use RO/DI for calibration. I doubt they would have stated that if it's not how you calibrate it.

You can doubt it all you want but if you'd like accurate results, you'll calibrate it with a 35ppt solution.

JustMe2Mc · Oct 4, 2016

What if you left your bottle of 35ppt open too long or it is old? You sure your 35ppt is accurate?

skim · Oct 5, 2016

AdamNC said:
The Red Sea states in the manual to use RO/DI for calibration. I doubt they would have stated that if it's not how you calibrate it.

They do say this in the instructions and it should be followed as the Red Sea was designed to read Sea Water. I have one and it works great I also have the Milwaukee Digital and it also is Calibrated with RO/DI. When Calibrated and tested against each other they read the same.

Ryan Rioux said:
I dislike the Red Sea refractometer a lot. Where can I find the calibration fluid.

What is there dislike, its the easiest one to read that I have ever seen and as for re calibrating after every use is not a must but to get the most accurate reading one can, this stands for all Refractometers. Believe it or not the most accurate are the long Glass tube ones. You take a sample out of the tank and float the unit in the sample but they are a pain in the butt.

madweazl · Oct 5, 2016

JustMe2Mc said:
What if you left your bottle of 35ppt open too long or it is old? You sure your 35ppt is accurate?

What if your RODI water spilled and you scooped it back into the bottle? What is your point?

They do say this in the instructions and it should be followed as the Red Sea was designed to read Sea Water. I have one and it works great I also have the Milwaukee Digital and it also is Calibrated with RO/DI. When Calibrated and tested against each other they read the same.

Would you expect them to read differently if they were both calibrated with 35ppt solution?

skim · Oct 5, 2016

This may help you understand why you get 2 different readings from the 2 units. It does not address the question of what to use for Calibration but like stated should explain the original question/post.

Ryan Rioux said:
Has anyone had experience with either of these products? I've recently used both. The Amazon ATC refractometer broke on me after the 2nd use , so I had to buy a Red Sea at a local store . 3x the money of the ATC. When I was measuring salinity with the ATC of my tank I was getting 1.023-1.024. When I am measuring with the Red Sea , I am getting the line that is 1.021-1.022. Both are required to be calibrated with Distilled or R/O water . Wondering if anyone has ever experienced 2 refractometers measuring different readings

http://www.redseafish.com/red-sea-salts/seawater-refractometer-salinity-test/

Randy Holmes-Farley · Oct 5, 2016

Ryan Rioux said:
I don't understand why the directions say to use distilled water to calibrate them. That's what I had been doing the whole time

Manufacturers make many of these to test sodium chloride brines, and in that use, they are intended for Ro/DI calibration. When using seawater, which many are not made for, that leads to miscalibration errors.