True seawater refractometer?

[Spare time]

Does anyone know if those cheap amazon refractometers (for $20) that say they measure seawater salinity actually do so and are not brine refractometers?


I just need a new one and don't feel like paying $80, and I have no way to tell if a company is lying about it or not.

 

[Randy Holmes-Farley]

Do you have a link to it?

 

[Snoopy 67]

Fish & Aquariums

www.nisupply.com

I've had mine for so long & it holds calibration very well.

 

[Spare time]

Do you have a link to it?

I'm on my phone at the moment so this is a screenshot of one but I can post a link in a bit.

 

[Spare time]

I may just buy the digital Hanna stick one but tests like that make me anxious as I have no clue how often they drift off of the calibrated number.

 

[19Mateo83]

I have an old marine depot one I purchased in 2009. It’s been well used and then in storage for 12 years. I checked it’s calibration against a LFS that uses a Milwaukee salinity checker and it was still spot on. I was surprised but apparently a redractometer will hold calibration of you take care of it.

 

[TokenReefer]

I verify/calibrate every time I use mine now because they sure can drift and correcting salinity take way more time than a calibration

 

[exnisstech]

That is the one I have been using for years. Needs calibration occasionally but I would buy another without hesitation. I have compared it to other units to verify the accuracy.

 

[TokenReefer]

Correct me if I'm wrong but if you're using a 35 ppt standard I don't see a difference between that one and the more expensive ones... What am I missing?

 

[exnisstech]

I may just buy the digital Hanna stick one but tests like that make me anxious as I have no clue how often they drift off of the calibrated number.

I have the Hanna HI98319 and it is not accurate compared to 3 refractometers. Its useable because it doesn't drift but it is 0.02 low so I just compensate

 

[Randy Holmes-Farley]

Correct me if I'm wrong but if you're using a 35 ppt standard I don't see a difference between that one and the more expensive ones... What am I missing?

Well, that's like saying if my cheap one is accurate, what is better about a more expensive one. Lifetime? Frequency of recalibration? Ease of use?

 

[TokenReefer]

Lifetime? Frequency of recalibration? Ease of use?

Yes I agree. These would most likely be the differentiating factors. But as long as the standard is accurate can't the same level of accuracy be achieved? I just can't think of why it wouldn't..

 

[Randy Holmes-Farley]

I'm suspicious that the refractometer pictured above is not really a true seawater refractometer.

The two different scales do line up for a sodium chloride solutiona nd do not line up for a seawater solution,.

hence, IMO, it is a brine refractometer and should be calibrated with a 35 ppt stadnard and NOT RO/DI or any other fresh water source.

 

[ilikefish69]

I may just buy the digital Hanna stick one but tests like that make me anxious as I have no clue how often they drift off of the calibrated number.

you will not be upset about your purchase. It comes with calibration fluid. If you rinse it in RO after every use it will only need calibrated monthly.

I am not sure if this is a bad idea or not, but I just grabbed some of my 1.026 tank water and keep it in a jug and use it as calibration fluid. ICP test came back matching exactly what I had been under the impression of. 100% recommend. Don't waste your time with the refactometers they will get rusty and a royal PITA

 

[Randy Holmes-Farley]

you will not be upset about your purchase. It comes with calibration fluid. If you rinse it in RO after every use it will only need calibrated monthly.

I am not sure if this is a bad idea or not, but I just grabbed some of my 1.026 tank water and keep it in a jug and use it as calibration fluid. ICP test came back matching exactly what I had been under the impression of. 100% recommend. Don't waste your time with the refactometers they will get rusty and a royal PITA

What salinity is the calibration fluid?

 

[Nman]

Mine was bought when they first came out in uk my LFS it wasn’t that cheap at the time carnt remember how much but still in use today . Still very accurate. Make is by TMC my calibration is water with a screw you turn to 0 and that’s it

 

[ilikefish69]

What salinity is the calibration fluid?

the Hanna came with 35 PPT , I just have about a gallon of my tank water that was ICP tested as the back up when I run out of the Hanna packets. I believe there were 6 included

 

[Randy Holmes-Farley]

the Hanna came with 35 PPT , I just have about a gallon of my tank water that was ICP tested as the back up when I run out of the Hanna packets. I believe there were 6 included

Sorry, I thought you were talking about the refractometer of the OP when you said it came with fluid. That Hanna fluid should be fine for the Hanna if made properly.

 

[Spare time]

I'm suspicious that the refractometer pictured above is not really a true seawater refractometer.

The two different scales do line up for a sodium chloride solutiona nd do not line up for a seawater solution,.

hence, IMO, it is a brine refractometer and should be calibrated with a 35 ppt stadnard and NOT RO/DI or any other fresh water source.

So it's really only a tiny bit off when calibrated to 35ppt right? At least that's what I remember from your article

 

[Tony Thompson]

What are the critical or safe boundaries regrading salinity in a reef aquarium? and how does this effect ones consideration with regards general accuracy when purchasing test equipment. ?

I was of the understanding that a range of between 29 ppt to 39 ppt was within a safe boundary. ?

Just for sake of interest, I like to have a robust piece of test equipment if possible. I liked the DD refractometer (around £45) and for my shop I used the Hanna HI 933000 conductivity meter (around £600). I also had a range of calibration samples.

Hobby kit tends to get thrown around so I advise a robust bit of kit that is within budget. Automatic temp compensation and a clear reading scale may also help.

The TMC refractometer mentioned earlier I had a number of these returned to my store broken, I stopped selling them.

I still don't understand why some people calibrate their refractometer at 0. I always use 35ppt. Can you shed some light on this @Randy Holmes-Farley