RO/DI refractometer calibration way off?

O

o0jmadr0x0o

New member
So today i picked up some Hannah salinity calibration fluid and put it in my refractometer Iwas shocked to see it show 25ppt!

I had been calibrating using my ro/di water to 0

I tested with two different refractometers and both showed the 10ppt difference. I set the meter to the calibrations fluids 35ppt and tested my ro/di and it showed 10ppt!

anyone know whats going on here?
 
Some refractometers have instructions to calibrate with RO (Milwaukee maybe?). I would still check it with a 35ppt standard after calibration.

In general, since it's a one-point calibration, you want to calibrate with the standard closest to what you are measuring. I would never recommend calibrating with RO water.

What refractometer are you using?
 
That's why you never calibrate with ro/di/distilled water when your sample is salt water.....always calibrate in the range that you will be using the refractometer at. If you were testing your tap water then it would be a good idea to calibrate with ro/di.....

Your difference of 10 ppt does seem very extreme !!!! 2-3 ppt is more reasonable
 
They are Bulkreefsupply refractometers.

I just tested my tap vs ro/di and its was 11ppt for tap and 10ppt for ro/di

I have been struggling with this tank for so long and I will be so relieved if this was the reason. But everything im reading is that it would only be 2-3 ppt off. is it possible for my tap water after filtering would show such high numbers, is it possible the Hannah solution is off?
 
Or do refractometers just stop working correctly over time, being dropped, or something along those lines?

I didnt consider this much because both meters I have read the same with the calibration fluid but trying to eliminate possibilities before raising the salinity in my tank 10ppt
 
I would bring a water sample to your lfs to double check.

Or you can make your own calibration fluid with table salt.
 
While I am never overly concern with .002 variance, stability remains the key to success. Corals can adapt to slight fluxs but hate change.

Your refractometer seems like it is not measuring.....get second opinion first.

I am one of those crazies who does calibrate with RO to zero.

Even with 35 calibration, the tools themselves are not that accurate and when it reads calibrated, your 1.0255 could be actually 1.024 or 1.026.

Over the years, I have found, by either calibration, when professionally tested, the difference is small.

Again, keeping that number stable always is key
 
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So I brought both meters to the LFS. after a bunch of testing and re-calibrating, both meters were still showing the same +10ppt on distilled water and saltwater(compared to their Hannah meter). I ordered a new one, should have it tomorrow to check what my tanks salinity is actually at!
 
May as well use a potato to test salinity if you don't calibrate your refractometer. If it's off that far with RODI I would be concerned but I always use cal fluid. It usually fluctuates regularly based on temps (even if it's ATC) so I calibrate every time I use it.
 
Got the new meter today.... Calibrateted with a Hannah 35.00ppt pouch as soon as i got it, checked my ro water and got 10!! I dont know what to do anymore!!!

The instructions do say to calibrate with distilled water to 0 and did that, checked the calibration fluid and got 25 ahhhh!
 
I'm not familiar with that calibration fluid but... there are three types. One for conductivity probes, one for refractometers, and one for both. I suspect that cal fluid is only for conductivity since it is for the Hanna HI98319 and not specifically refractometers.

If it is for a conductivity probe it would read 35ppt on the probe but 31.6ppt on a refractometer. This is what I use, it will work with both... I'd consider ordering a bottle.

https://smile.amazon.com/Aqua-Craft...encoding=UTF8&*Version*=1&*entries*=0&ie=UTF8
 
o0jmadr0x0o said:
Got the new meter today.... Calibrateted with a Hannah 35.00ppt pouch as soon as i got it, checked my ro water and got 10!! I dont know what to do anymore!!!

The instructions do say to calibrate with distilled water to 0 and did that, checked the calibration fluid and got 25 ahhhh!
Click to expand...


How are you cleaning the meter between readings?
 
tkeracer619 said:
I'm not familiar with that calibration fluid but... there are three types. One for conductivity probes, one for refractometers, and one for both. I suspect that cal fluid is only for conductivity since it is for the Hanna HI98319 and not specifically refractometers.

If it is for a conductivity probe it would read 35ppt on the probe but 31.6ppt on a refractometer. This is what I use, it will work with both... I'd consider ordering a bottle.

https://smile.amazon.com/Aqua-Craft...encoding=UTF8&*Version*=1&*entries*=0&ie=UTF8
Click to expand...


Yup. this was the problem. I wish the LFS had noticed the Hannah pouches are for conductivity and not salinity!!!!

So back to trying to figure out why my tiny tank with tiny frags is using so much ALK and Cal
 
BTW - One clue here is your tap water reading. 11 parts per thousand is 11,000 ppm. No municipal city water source anywhere has a hardness anywhere near that high. Typical in the Eastern US would be somewhere between 50 ppm to 300 ppm (and 300 ppm would be unusually high). Some Western US cities have "liquid rock" in the range of 700 - 900 ppm.

I suppose it's a bit late for this since you've already ordered one, but a better bet would've been the Milwaukee MA887. No interpretation, and automatic temperature compensation.

Edit: By the way, if you want an ultimate sanity check, and you have an accurate kitchen scale (every reefer needs one of these, btw), you can get a 1 liter class-A volumetric flask off of Amazon for about $25. When filled with 35ppt seawater to the calibrated mark, and tared for the flask weight, it will weigh 1,026 grams at 20 deg C (68 deg F). It will be off very slightly if you fill it with 78 deg F tank water - it will weigh 1,025 grams.
 
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o0jmadr0x0o said:
Yup. this was the problem. I wish the LFS had noticed the Hannah pouches are for conductivity and not salinity!!!!

So back to trying to figure out why my tiny tank with tiny frags is using so much ALK and Cal
Click to expand...

Awesome, glad that resolved it!

Check your pumps, if there is calcification on the internals, you could precipitating out your alk and cal.

I have a RSM130 I use for coral and inverts and I had to put a calcium reactor on it. Otherwise I was testing and dosing daily. The alk and cal was all over the place. No idea why but that tank precipitates like crazy. Once moving the calcium reactor it's stable.
 
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