# Salinity Meter (Hydrometer) vs. Refractometer



## MediaHound (Jul 19, 2006)

So I finally got a refractometer after all these years 

I placed a couple drops of RO / DI water on it, and calibrated it at 1.000 (it was reading just a hair higher).

I then placed a couple drops of water from my reef on it, and the reading was 1.028 (edit - I got the saline solution to calibrate it properly)

My trusty salinity meter had a reading of 1.024 whereas my refractometer read 1.028 

Wish I had one of these sooner, my salinity level is a tad bit high!


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## Galibore (Feb 20, 2008)

*Re: Salinity Meter vs. Refractometer*

Hey MediaHound,

I had exactly the same problem. Although not as hi as yours but my hydrometer was way out.

One thing I have learned though and is not always stated in the instructions; if your refractometer does not have *A*utomatic *T*emperature *C*ompensation is that your R.O water with which you calibrate have to be the same temperature as the water to be tested.

All in all, I think my refractometer rocks!! What brand did you get?


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## MediaHound (Jul 19, 2006)

*Re: Salinity Meter vs. Refractometer*

Hey there! I got this one: 
Cultivated Coral
It does not have a manufacturer name on it, but I do know the model is the RHS-10ATC. This model does have automatic temperature compensation (ATC). 

I was really surprised at how high my salt level was, and now I can push my water parameters to that next level of perfection  Rock on!



And I have scanned in the instructions in case they are useful for anyone with the instrument and no instructions.


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## Galibore (Feb 20, 2008)

Mine is a ReefOctopus, but doesn't have ATC 

Have you read the article by Randy Holmes-Farley regarding salinity?

I have had a millepora on the brink of death (due to a seperate issue). It never quite recovered until I read that article (now if only I can find it again...)

Anyway, the instructions by synthetic salt manufacturers always state to have your salinity (and I use this term liverally) at about 1.023. But Randy Holmes-Farley recommends 1.026 as this is closer to the NSW level.

So I slowly raised my salinity to 1.026 and lo and behold, my Millepora started recovering. Not saying its because of the raised salinity, but it sure had something to do with it.

Sorry for going a bit off topic here, but thought it would be interesting.

And thanks to my refract. I can now keep my salinity stable at exactly 1.026


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## cultivatedcoral (Jul 7, 2007)

Hi Galibore,

Yes, for saltwater fish only, 1.023 salinity is better but corals usually a little higher 1.025-1.027. Just like you said, near NSW.

Good luck with the Mille. They are great corals. Hydrometers just don't cut it anymore when dealing with corals. Refractometer of a salinity probe is even more convenient.

Take care.

Nick DeBellis
Cultivated Coral
Cultivated Coral Inc.


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## cultivatedcoral (Jul 7, 2007)

Thanks for the plug Jarred. I've just hooked up with a guy who can get me some rare saltwater fishes (hopefully). It's still not a done deal. But it appears I can get Blue line angels, Bandit angels, Interrupta angels, Wrought Irong Butteryflys, Conspicuous angels, west african angels etc. 

Now I'm looking into setting up a holding/quarantine system. 

Something like this would be perfect but I need to get the ok from the ole ball and chain. haha. Ya know what I mean.Benchtop Systems for small classroom and lab applications involving the research of Zebrafish and Xenopus species

Talk to you soon.

Nick DeBellis
Cultivated Coral
Cultivated Coral Inc.


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## MediaHound (Jul 19, 2006)

Those are amazing fish Nick! Can't wait to see them if you do. 

And that holding system is pretty nifty, it would certainly get you started along this path (not mine, heh): 










 

Here's another manufacturer: 
Tecniplast SPA - aquatic systems - ZEBRA FISH HOUSING SYSTEM

Catch you later!


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## goldenmacman (Jun 12, 2008)

i just use a reg. hydrometer, does the job fish and coral are fine.. i take the water to be tested once a month to my local fish store where they use a refractometer... i dont think its worth the money...


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## maqo.org (Jun 28, 2008)

One thing to keep in mind is that if you are going to be testing water above 1.015 you really want to use a slightly saline solution to calibrate your refractometer. Most of them are 1.007 or 1.015. I did the same thing when I first got a refractometer and found that calibrating at 1.000 had me off .002 when I tested normal saltwater


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## racermike27 (Jul 6, 2008)

Jarred,

What was mentioned about calibrating with a slightly saline solution is true. I did the same thing and found my refractormeter was off by a little as well.


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## MediaHound (Jul 19, 2006)

Thanks alot for confirming this Mike! 
And thank you very much maqo for suggesting it initially. 

"Slightly" is a little ambiguous when it comes to calibration though! 
Is there some more exact way to do it? How slightly saline are we talking and how do I get it there? Example, how many grams of salt in a liter of RO/DI, or whatnot..?


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## racermike27 (Jul 6, 2008)

Jarred,

You can buy the calibration fluid from places like premiumaquatics.com etc....
It can also be made but I don't have the original link anymore.

I think pinpoint may make the solution...

-Mike


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## MediaHound (Jul 19, 2006)

Thanks, I will get it. Much appreciated guys.


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## maqo.org (Jun 28, 2008)

The two different solutions that I have used are from pinpoint, and I'm not sure of the other one, but they are different salinities (1.007, and 1.015) and I normally use both of them once or twice a year to get the calibration down solid and then just use the 1.015 to make sure it is not falling off. 

Another thing to keep in mind is that your calibration fluid needs to be at the right temp (which should be in the instructions) even if you have an ATC. I didn't know this at first and couldn't figure out why my refractometer kept straying. I was using it in a greenhouse and the temp would fluctuate wildly, now I keep it inside and it is fine.


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## rendos (Nov 9, 2008)

I can't believe people still use swing arm hydrometers.
Word of caution - if you use a refractometer, please do yourself a favor and calibrate it occassionally with salinity calibration solution.
Refractometers get out of cal also.


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## drhank (Aug 3, 2009)

I've used a simple bulb hydrometer for over 25 years with no problems.


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## WhisperinLoudly (May 27, 2009)

Although these are better than the swing arm, imo it would be a pain if you have a lot of surface movement to try to get a good reading unless you take some water out of the tank and test it that way. Just wondering how you do this without shutting off all the powerheads. Don't get me wrong Doc, I' not talking bad about the bulb hydrometers as I used one before I got my refractometer. I just think once you get the refractometer calibrated they are a lot easier. This like everything that comes out of my trap is only my opinion.


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## nina-zh (Jul 23, 2010)

*Re: Salinity Meter vs. Refractometer*



MediaHound said:


> Hey there! I got this one:
> Cultivated Coral
> It does not have a manufacturer name on it, but I do know the model is the RHS-10ATC. This model does have automatic temperature compensation (ATC).
> 
> ...


this instrument is a good instrument for aquarium fish,I know some manufactures about this refractometer.this is a low cost and useful instrument.


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## nina-zh (Jul 23, 2010)

MediaHound said:


> Thanks alot for confirming this Mike!
> And thank you very much maqo for suggesting it initially.
> 
> "Slightly" is a little ambiguous when it comes to calibration though!
> Is there some more exact way to do it? How slightly saline are we talking and how do I get it there? Example, how many grams of salt in a liter of RO/DI, or whatnot..?


Salinity RHS-10ATC

maybe you can get what you want here!


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## nina-zh (Jul 23, 2010)

MediaHound said:


> Thanks alot for confirming this Mike!
> And thank you very much maqo for suggesting it initially.
> 
> "Slightly" is a little ambiguous when it comes to calibration though!
> Is there some more exact way to do it? How slightly saline are we talking and how do I get it there? Example, how many grams of salt in a liter of RO/DI, or whatnot..?


Salinity RHS-10ATC

maybe you can find what you want here!


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