Trouble reading Refractometer

Lacrette1991 · Mar 13, 2020

Hey guys. Forgive me for using a hydrometer for so long but finally picked up a refractometer off amazon last weekend. I’ve been struggling to figure out if my refractometer is broken or if I’ just don’t know exactly what I’m looking for. I had my aquariums SG at 1.026 using the fluval hydrometer but here in the photos you will see my readings.
Using coralife marine salt and 5 gallon bucket to mix at 78°.
The calibration fluid says it’s set to 35ppm but my reading for the 1/2 cup of salt per gallon is way above 1.026 on my refractometer.
Everything seems to be doing just fine in my tank but I have no idea what my SG really is as I’m sure you all know hydrometer aren’t know you be very accurate.
Thoughts?

Super Fly · Mar 13, 2020

Did u first use the calibration fluid to adjust ("calibrate") the refractometer to 1.025 prior to using refractometer to test tank water? The hydrometer giving high reading using calibration fluid prob means the hydrometer has become out of calibration. When I use to use hydrometer, I'd rinse it w fresh water after each use while letting it sit in clean water in between to prevent miscalibrations.
Also, temp of refractometer can affect reading even if it says ATC. Try to maintain similar temp to tank water, i.e. don't leave in basement.

Lacrette1991 · Mar 13, 2020

Super Fly said:
Did u first use the calibration fluid to adjust ("calibrate") the refractometer to 1.025 prior to using refractometer to test tank water? The hydrometer giving high reading using calibration fluid prob means the hydrometer has become out of calibration. When I use to use hydrometer, I'd rinse it w fresh water after each use while letting it sit in clean water in between to prevent miscalibrations.
Also, temp of refractometer can affect reading even if it says ATC. Try to maintain similar temp to tank water, i.e. don't leave in basement.

I first used the calibration fluid which says to set it at 35ppt but I was doing some reading and I think I missed that 35ppt is 1.025. Going to recalibrate and see what my readings are.

jstephens24 · Mar 13, 2020

I know you just bought it but Hanna makes a pretty good digital readout one I have heard.

Lacrette1991 · Mar 13, 2020

Super Fly said:
Did u first use the calibration fluid to adjust ("calibrate") the refractometer to 1.025 prior to using refractometer to test tank water? The hydrometer giving high reading using calibration fluid prob means the hydrometer has become out of calibration. When I use to use hydrometer, I'd rinse it w fresh water after each use while letting it sit in clean water in between to prevent miscalibrations.
Also, temp of refractometer can affect reading even if it says ATC. Try to maintain similar temp to tank water, i.e. don't leave in basement.

So after re calibration. This is my reading on my freshly mixed salt water. Used 3 cups of salt in 5 gallons and I’m now at 1.025!
Thanks for clearing that up!

Sailingeric · Mar 13, 2020

You cannot use a beer refractometer. My understanding is that their is difference in scale. I have both the beer one and salt water one since I brew beer. I have not compared but I would get the right tool and send that one back if it was sold for SW.

Sailingeric · Mar 13, 2020

Lacrette1991 said:
Hey guys. Forgive me for using a hydrometer for so long but finally picked up a refractometer off amazon last weekend. I’ve been struggling to figure out if my refractometer is broken or if I’ just don’t know exactly what I’m looking for. I had my aquariums SG at 1.026 using the fluval hydrometer but here in the photos you will see my readings.
Using coralife marine salt and 5 gallon bucket to mix at 78°.
The calibration fluid says it’s set to 35ppm but my reading for the 1/2 cup of salt per gallon is way above 1.026 on my refractometer.
Everything seems to be doing just fine in my tank but I have no idea what my SG really is as I’m sure you all know hydrometer aren’t know you be very accurate.
Thoughts?

Good reading but near the bottom and at your Brix reading, you are closer to 45-50 PPM of salt. way to high!!!

Refractometers and Salinity Measurement - REEFEDITION

Title photo by R2R member Rskillz By Randy Holmes-Farley Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions Read more here...

www.reefedition.com

Lacrette1991 · Mar 13, 2020

Sailingeric said:
You cannot use a beer refractometer. My understanding is that their is difference in scale. I have both the beer one and salt water one since I brew beer. I have not compared but I would get the right tool and send that one back if it was sold for SW.

This is the refractometer I’m using. Looks like other salt water refractometers I’ve seen.

Sailingeric · Mar 13, 2020

Lacrette1991 said:
This is the refractometer I’m using. Looks like other salt water refractometers I’ve seen.

they all look about the same but the pic you posted show Brix (measure of sugar in the liquid) and wort. Wort is sugary liquid from grains when making beer before the yeast do their part. Starting SG minus ending SG is your ABV, but the scale is different for salt water. If you have fish or corals in your tank I would be worried your salinity is too high.

Sailingeric · Mar 13, 2020

If you want to learn how to start making beer, you do have a head start on the equipment. Just need a big pot and plastic bucket with a lid.

Lacrette1991 · Mar 13, 2020

Sailingeric said:
they all look about the same but the pic you posted show Brix (measure of sugar in the liquid) and wort. Wort is sugary liquid from grains when making beer before the yeast do their part. Starting SG minus ending SG is your ABV, but the scale is different for salt water. If you have fish or corals in your tank I would be worried your salinity is too high.

You are 100% correct. Idk how I missed this when ordering...sending it back today.

Cory · Mar 13, 2020

Hey with approximately 780 grams in 5 gallons gives me 1.026 sg

Lacrette1991 · Mar 13, 2020

Cory said:
Hey with approximately 780 grams in 5 gallons gives me 1.026 sg

That’s 2.86 cups. Do you weigh your salt?

GoVols · Mar 13, 2020

Lacrette1991 said:
I first used the calibration fluid which says to set it at 35ppt but I was doing some reading and I think I missed that 35ppt is 1.025. Going to recalibrate and see what my readings are.

Calibrate it to .35ppt not 1.025 SG, their not the same.

Cory · Mar 13, 2020

Lacrette1991 said:
That’s 2.86 cups. Do you weigh your salt?

I did once for this purpose and found most people use around that much. Now i test via refractometer and do not weigh, but yes about 3 cups when the water is 1 figer from the top of a bucket.

K7BMG · Mar 13, 2020

Just a note when you order your replacement refractometer.
Be sure to buy some calibration fluid.
BRS and Marine Depot both sell it, probabily find some on Amazon as well. Its cheap but more accurate than testing your own mix.