Correct solution to use to calibrate refractometer

[Mightyfish]

I read in this forum and also reef keeping issues that we should use a solution of 35ppt to calibrate refractometer because thats what we want to measure, despite that most refractometer comes with an instruction to use RO DI water. Thats what i have been using to calibrate in the past year. However i recently posted this matter on our local (Australian ) marine facebook site i received an overwhelming response that everyone is using RO DI water to calibrate instead which made me doubt myself. So am i correct to use 35ppt solution and when using it i will adjust refractometer screw at 1.026 mark and thats the end to calibrate it correctly?

 

[shifty51008]

Yes you are correct, use the 35ppt solution and set your refractometer to 35ppt or 1.026. Whenever you calibrate something you want to calibrate it to as close to what your final endpoint is. Same when calibrateing a pH meter, you want to use calibration solutions close to 8.

Hope that helps and made some sence as i am half asleep lol

 

[Mightyfish]

Yes you are correct, use the 35ppt solution and set your refractometer to 35ppt or 1.026. Whenever you calibrate something you want to calibrate it to as close to what your final endpoint is. Same when calibrateing a pH meter, you want to use calibration solutions close to 8.

Hope that helps and made some sence as i am half asleep lol

Thanka for confirming my thought. Is there some concrete article that i can show the other reefers on this Australian facebook page that 35ppt is the correct solution to use? I guess that refractometer in Australia and US are the same tool.

 

[Ron Reefman]

Try calibrating your refractometer with RO/DI water and then compare it to the 1.026 calibration fluid. If it's off, you'll have personal proof. If it's still spot on, then you'll know that your refractometer can be calibrated accurately enough with RO/DI or 1.026 calibration fluid. That does NOT mean that all refractometers can be calibrated with RO/DI, just that yours can.

I for one would like to hear your results (and anybody else who tries the experiment). I'll add my results after some others try it with theirs.


Personally, I calibrated mine with calibration fluid and then tested tank water with it and with my cheap hydrometer. My hydrometer was 0.004 low. So I made a label that said "ADD 0.004" and put it on the hydrometer. That was over 4 years ago. Since then I have re-calibrated my refractometer 7 or 8 times (every 6 months) and it's always close to right, but almost always not quite. Every time I do the calibration I compared it with my hydrometer and it was always EXACTLY 0.004 low every time. Hydrometers are not 'accurate' from the factory, but once calibrated and labeled they seem to stay spot on. And personally, I find the hydrometer much quicker and easier to use and clean after I'm done testing.

 

[gone fishin]

Most refractometers only use a one point calibration. So you want to calibrate it as close to what your ultimate setpoint is, in this case 35ppt. If you ever decided to use hyposalinity for some reason then use RO/DI since you would want something close to 1. Just my 2 cents worth, good luck

 

[russ265]

you have a bad refractometer if you need a solution to get an accurate reading.

ro water will always be 0.

your hydrometer was low because it is generally calibrated at a temperature below tropical aquariums.

 

[shifty51008]

http://reefkeeping.com/issues/2006-12/rhf/index.php#11

 

[russ265]

http://reefkeeping.com/issues/2006-12/rhf/index.php#11

stated the exact same thing.
refractometer is shot

 

[gone fishin]

you have a bad refractometer if you need a solution to get an accurate reading.

ro water will always be 0.

your hydrometer was low because it is generally calibrated at a temperature below tropical aquariums.

Most refractometers need periodic calibration. IME any instrument will and can drift requiring calibration.

 

[russ265]

Most refractometers need periodic calibration. IME any instrument will and can drift requiring calibration.

i think cheaper ones do. bumping and dropping the refractometer will definitley jostle it. however if you calibrate with 35 ppt and ro water isnt 0... there is no question, the refractometer is done.

sure you can bandaid it and use that calibration fluid to be MORE accurate, but it will drift and be off more and more as you continue using it.

i havent calibrated my refractometer in 5 years and ro water still reads 0

 

[shifty51008]

i think cheaper ones do. bumping and dropping the refractometer will definitley jostle it. however if you calibrate with 35 ppt and ro water isnt 0... there is no question, the refractometer is done.

sure you can bandaid it and use that calibration fluid to be MORE accurate, but it will drift and be off more and more as you continue using it.

i havent calibrated my refractometer in 5 years and ro water still reads 0

What refractometer do you use?

 

[russ265]

What refractometer do you use?

im not at the house to see the brand.
it isnt anything special though.

tbh. if you have a decent refractometer you will have bigger salinity swings through evaporation more than anything else.

 

[gone fishin]

im not at the house to see the brand.
it isnt anything special though.

tbh. if you have a decent refractometer you will have bigger salinity swings through evaporation more than anything else.

I have extremely small salinity swings due to ATO.

 

[gone fishin]

i think cheaper ones do. bumping and dropping the refractometer will definitley jostle it. however if you calibrate with 35 ppt and ro water isnt 0... there is no question, the refractometer is done.

sure you can bandaid it and use that calibration fluid to be MORE accurate, but it will drift and be off more and more as you continue using it.

i havent calibrated my refractometer in 5 years and ro water still reads 0

I guess we are just going to have to agree to disagree on this point.

 

[shifty51008]

http://blog.captive-aquatics.com/ca...bration-the-myth-and-risks-of-using-rodi.html

Another good read on why to use a calibration fluid and not rodi water

 

[russ265]

http://blog.captive-aquatics.com/ca...bration-the-myth-and-risks-of-using-rodi.html

Another good read on why to use a calibration fluid and not rodi water

this is not even a debate.

if you use calibration solution and rodi is greater or less than 1 off, you would be better off using a hydrometer. it is just mathematically dis ingenuous to say otherwise.

its a faulty device

 

[russ265]

I guess we are just going to have to agree to disagree on this point.

there is nothing to disagree about. ro water is 0. whether your refractometer states so or not.

 

[gone fishin]

I have no inclination to argue about it. I will still recommend to folks that ask, they need to periodically calibrate their refractometers with 35 ppt fluid. Have a good day.

 

[Chicago]

When I calibrate with calibration solution at 35 ppt. And then check rodi water I get less then zero. Like .003 less .. Put another way it is below the scale.

When I calibrate with rodi to zero I get a read of like 1.030 when I test the 1.026 calibration solution.

By the way this is happening on two brand new brs refractometers. I have tried it on two different bottles of calibration solution.

This is so messed up because I am doing hypo and the salinity might not be 1.009 but rather 1.006. Two fish missing.