New refractometer - can't trust it

Pokerman11

Pokerman11

Member
I have a Living Sea Hydrometer 30CM
Two different styles of Red sea swing arm
And a new refractometer I purchased from BFS along with the pinpoint calibration solution. Note I use refractometers for my other hobby (bee keeping) so they are not new to me, not that I still might be screwing this up just that I use them often in the past.


The calibration solution and refractometer mentions 20C, so I have the calibration solution at 20C (68F) and calibrate my refractometer to 1.026 as per instructions. It's a fresh bottle just opened.


The issue I am having is the refractometer with the new calibration solution is way different than my hydrometers.

When I test my DT water here is what I get:
Refractometer 1.0300
Living sea hydrometer 1.0250
Red Sea hydrometer #1 1.0255
Red Sea Hydrometer #2 1.0245


My tank is at 76F so I know there is some differences related to temperature. but these are extreme.

So is the pinpoint solution bad? The refractometer or my hydrometers?

I guess I take them down to a LFS and let them give me a reference. Just confused on how to get a good Specific grav reading.

I know there are a lot of horror stories about the swing arm hydrometers, but I've had good luck with them backed up with a glass hydrometer.

I gota believe that this refracotementer is off - but I'm now lost.


Refractometer off?
 
You could test the refractometer against another one but I would trust the refractometer before the swing arm.
 
If it were 1 hydrometer vs 1 refractometer, I'd trust the refractometer. The fact that 3 hydrometers are all reading within 0.01 of each other while the refractometer is roughly 0.5 off from them is cause for concern and warrants further investigation.

It could very well be that they are all off by 0.5, but I wouldn't be quick to jump to that conclusion.
 
I had a similar situation and found my calibration solution was off. I made up some DIY calibration solution then tested against distilled water followed by the DIY calibration solution and my refractometer is now in line with my other testing devices.
 
I agree with the above, though I have no way to get to a solution....maybe order a different brand or a couple calibration solutions
 
I would bring it to your LFS and test your refractometer and also theirs on their tank water. Also try testing on RO water and see if you show zero.
 
I don't get 0 on RO if calibrated on mine, I used to use RO to calibrate....who the hell knows where it's actually at now, can't use RO don't know if you can trust the calibration solution etc etc
 
If you test with RO water if calibrated with correct solution it will likely read less than 1.0. If you read higher like 1.005 then it would indicate the unit is either defective or improperly calibrated.
 
I would get some different calibration fluid and recalibrate.

I have two refractometers, and two different bottles of calibration fluid. My Pinpoint fluid is probably at least 3 years old. I haven't used the Pinpoint in over a year, but have been using a different brand calibration fluid that came with my newest refractometer.

Remembering this thread, after doing some testing last night, I checked the Pinpoint fluid on a refractometer that was calibrated with the other solution. The Pinpoint fluid read 1.030. It should've read about 1.0265ish (35 ppt). I cleaned everything and checked again. 1.030 for sure. I checked the other calibration fluid... 35 ppt right on the nose. In addition, I've been making my own saltwater for years using the same exact quantity of water and salt. Every. Single. Time. And it always comes out the same salinity. So I'm pretty sure of the accuracy of my refractometers, just based on that salt water.

I'm not really sure why the Pinpoint solution is reading 1.030. Years ago, when I was using it, it read fine... I calibrated things using it and it matched what I knew my saltwater was at. I keep the solution capped and don't cross contaminate it. Calibration fluid shouldn't go bad as it gets old - unless it evaporates - so I'm not really sure why it's not accurate anymore.

Regardless... thought I'd pass on the story and advice the OP to get a different brand calibration solution before making any changes. While I'd trust a refractometer over a swing-arm 10 out of 10 times, the fact you've got three swing-arms saying the same thing and the refractometer waaaaaay off is a concern.
 
Just a point of clarification. The Living sea hydrometer is one of those 30CM tall GLASS floating hydrometers. It's not a swing arm. I have to believe it is the most accurate thing I own.

I'll try to hit the LFS and see what comparison readings I can get. At this point I think that pinpoint calibration fluid is off.
 
I agree regarding the floating hydrometer. Assuming you've compensated correctly for temperature, it's definitely the most accurate thing. I would definitely suspect bad calibration fluid.
 
At my LFS took in water as well as my equipment.

The refractormeter is correct.

The floating hydrometer is off, and a well as my swing arms (which are really old so I did not trust them anyway)
 
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