HELP! Red Sea Refractometer Calibration

[SPR]

I have been using this piece of kit since my first tank in February 2016 and trusted it completely. I am new to aquariums so bought what I believed to be the best.

Recently the readings have been fluctuating wildly. I had been maintaining salinity at 35ppm and all other parameters were spot on for my new tank or at least I thought. I had initially put this down to high temperatures here in the UK and the tank is currently at around 28-29C

The salinity readings have gone from consistent with minor fluctuations to a sudden apparent drop from 35ppm to 25ppm 3 days which led me to dump a load of salt into the tank to bring it back up.

I then start reading on the Internet about these and calibrate the Refractometer with RODI to 0 and when I test the water is 44ppm+! So been changing water to bring it back down. Fortunately or hopefully no harm has been done as I did it slowly.

Over the last few days I have been using the Refractometer and before each use checking back to 0 with RODI and I find that I have to adjust it on virtually every check to get it to read 0. I have read reviews etc and many seem to have the same problem with this. It will also vary by maybe 1 ppm with 2 consecutive tests

Any comments or experience would be greatly appreciated ? I know it's sold as a precision piece of kit but it won't seem to hold its calibration... Now I am aware of this I can deal with it but..

 

[DaveK]

Generally you should not need to calibrate a refractometer very often. Once it's set it usually holds the calibration well.

You can calibrate it with RO/DI water if the water has a TDS reading of 0. That's asking a lot though. I think your much better off using a calibration solution for SW that is designed to calibrate to 35 ppt or s SG of 1.026, since this is closest to the SW level you usually want.

Here is one example of such a calibration solution (offsite) - http://www.bulkreefsupply.com/aqua-craft-refractometer-calibration-fluid.html

What I do it test the calibration with that solution and then double check it with RO/DI water. If bothe are reading right, I know I'm calibrated correctly.

When you use a refractometer you must be sure the water testing area is completely clean and your test sample has no bubbles in it.

I have never had a problem with consecutive readings of the same sample being off. Possibly something is broken or loose on your refractometer?

 

[Big Pete]

Hi SPR

I have the same issue with the Red Sea Refractometer, I leave mine out the box overnight then test with RO water , calibrate as it always needs to be calibrated , I make sure the RO Water is at 25 degrees , after that I first check the tank water then check the newly mixed salt water.

I don't know if this helps but there you have it

Cheers

Big Pete

 

[SPR]

Thanks guys. Any tips on ones that dont need calibrating like this so often and are good?

I may end up just getting some of the 35ppm calibrating fluid but thats something else i need to trust to be spot on. I suppose i can compare this with the RO and if they match happy daya


Sent from my iPhone using Tapatalk

 

[DaveK]

Considering that the calibration fluid is only something like $7, it's cheep insurance to make sure your getting good readings.

 

[SalinFL]

When I used one, I now use Hanna to check salinity, I periodically washed mine out with Dawn dish detergent in addition to cleaning it with water. I found that just the one drop of detergent stripped away the salt residue that eventually would make the arm stick.

 

[mtamorrow]

I have to calibrate my Red Sea refractometer every week when I do my water change. Very disappointed. Have a generic brand that has only been calibrated once and is spot on.


Sent from my iPhone using Tapatalk

 

[DaveK]

A refractometer should hold it's calibration fairly well. Mine is not a Red Sea one, but I can say I only calibrate it every few months and usually I don't need to adjust it.

It might be worth a question in the Red Sea forum and ask @RedSeaKev about any calibration issues or other light they can shed on the subject.

One last trick, if your trying to match SG between say your tank and water change water, you don't need to calibrate the refractometer at all. Just measure the tank water and match the water change water to that. If the refractometer is out of calibration, it will be out the same amount for both, so SG will match.

 

[SPR]

Thanks. I have ordered some of the 35ppm calibration fluid and have already spoken with Kevin as he alerted me to the fact it needs calibrating on a regular basis and I think he said before each use as otherwise the results can vary by 1-3 ppm as its such a precise instrument. Kevin was very helpful with this along with another tank problem I had.

Will see how I get on and next time I visit my LFS I'll see what they use as well.

 

[DStaelens]

I have the same issue with mine, I can calibrate it and if I walk into another room with a temperature difference, it will swing quickly by a few ppm. I had an old generic one that would be rock solid. I would check it once a month at most and it was always spot on. Too bad I dropped it on a concrete floor...

Recently the readings have been fluctuating wildly. I had been maintaining salinity at 35ppm and all other parameters were spot on for my new tank or at least I thought. I had initially put this down to high temperatures here in the UK and the tank is currently at around 28-29C