Refractometer Reading

[ReefGirl87]

Ok guys- I thought I knew how to operate a refractometer- HOWEVER. I’m on my 3rd one thinking the first 2 were duds. I’m getting the same reading on all 3, but something totally different from my hydrometer. The refractometer is giving me a negative reading. I calibrated it to 0 with calibration solution. Cleaned it off then applied my tank water. My hydrometer is reading 31...what the heck am I doing wrong??!

 

[link81]

calibration solution? what did you use?
if you used 35ppt, you should set the refractometer to 35, not zero.

 

[Birdbrains?]

I just use a hydrometer .... I can't help... Did you do what link81 said ?

 

[ReefGirl87]

calibration solution? what did you use?
if you used 35ppt, you should set the refractometer to 35, not zero.

OMG. Thank you! I’ll try that! That’s my issue!

 

[link81]

only with RO water do you set it to zero. with the solution, you set it to 35.
easy mistake. no worries. we've all been there lol.

 

[Birdbrains?]

OMG. Thank you! I’ll try that! That’s my issue!

Okay, ReefGirl87 - remember to ask people inhere about stuff before you buy more gear !!

 

[ReefGirl87]

Okay, ReefGirl87 - remember to ask people inhere about stuff before you buy more gear !!

I definitely will!!

 

[ReefGirl87]

only with RO water do you set it to zero. with the solution, you set it to 35.
easy mistake. no worries. we've all been there lol.

Lol, for sure! I didn’t even think about the RO vs calibration solution! Thanks again! I got an accurate reading now! It is a little lower than my hydrometer, but it’s a lot closer than what it was! My refractometer says 27, hydrometer 32. Opinions on which is more accurate?

 

[link81]

with a calibrated refractometer, i can almost guarantee that it is more accurate then the hydrometer.

 

[ReefGirl87]

with a calibrated refractometer, i can almost guarantee that it is more accurate then the hydrometer.

Ok good to know, I’m going with those numbers then. Thanks again for your help!!

 

[link81]

i'm assuming that you're using a swing arm right? not a floating glass one?

 

[ReefGirl87]

i'm assuming that you're using a swing arm right? not a floating glass one?

Correct. Just an instant ocean swing arm hydrometer.

 

[link81]

yup, i thought so. definitely go by then refractometer then.
I don't calibrate every use, but fairly frequently. the solution is cheap.
Make sure you keep it capped though, if anything evaporates then the solution will be inaccurate.
i actually keep a few on hand just to cross check between all of them.

 

[Sailingeric]

Lol, for sure! I didn’t even think about the RO vs calibration solution! Thanks again! I got an accurate reading now! It is a little lower than my hydrometer, but it’s a lot closer than what it was! My refractometer says 27, hydrometer 32. Opinions on which is more accurate?

I would trust the refractometer. I have used hydrometer for making beer and suspect the same would apply for SW, any little air bubble or difference in temperature other than what it is calibrated for will make it off. Even the if the scale/ paper can be off in the tube. Usually with cheaper hydrometers you want to measure at the temp it is set for and note any difference so you can adjust later. Most refractometers self adjust for temp.

 

[Kresimir_72]

I use hi98319 marine salinity tester from hanna and no problem....It is one of best investment for my reef....

 

[shred5]

OMG. Thank you! I’ll try that! That’s my issue!

Only if it is 35 ppt calibration fluid... Most that comes with the refractometer is distilled water which means you should adjust to zero. 35 ppt Calibration fluid is better to use.

 

[Sailingeric]

I got mine from BRS and it said not to use distilled water, only 35 PPT fluid. The one I have for beer making is to use water to zero out, not a double imperial NE style IPA . If you get one, follow the directions

 

[Birdbrains?]

I only keep shoreline Cnidaria and I use the floating glass hydrometers and allow the tank parameters to swing pretty broadly compared to what deep sea lifeforms can handle, so I would definitely say that you should do as advised here and keep taking wellcalibrated readings across several refractometers to keep swings at a minimum.

The plastic hydrometers are practical when throwing together a saltwater mix that can be adjusted later on to appropriate values but I wouldn't use them for actual precision readings.

At least now you have several refractometers & having replacement gear always gives more peace of mind to enjoy the hobby