# Hydrometer vs Refractometer



## des (Jul 30, 2011)

Marine is all new to me. I'm using my Fluval Edge for a small marine setup.

To check the gravity/salinity what would you recommend?
Keep in mind that the opening on the Fluval Edge is small and I can not fit the traditional size hydrometer.

Is my best option a refractometer?
Do you guys know where I can get reliable ones that are not expensive?
I see them on Ebay but how reliable are these?


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## sig (Dec 13, 2010)

des said:


> Marine is all new to me. I'm using my Fluval Edge for a small marine setup.
> 
> To check the gravity/salinity what would you recommend?
> Keep in mind that the opening on the Fluval Edge is small and I can not fit the traditional size hydrometer.
> ...


you can not compare two. Hydrometers are not accurate

http://www.aquariumsupplies.ca/salinity-refractometer-p-2582.html?osCsid=pf46rrqplltop5tatt4er3qae5

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## altcharacter (Jan 10, 2011)

You'll find out really quick with tanks under 10 gallons that it's not going to matter what your salinity is everyday due to evaporation. My salinity in my 6 gallon would be .024 in the morning and by the time I came home from work it might be .026. A refractometer would be nice if you could get one but a hydrometer would work for your setup due to how small it is even though they're not as accurate. I take 3-4 readings on my hydrometer when I change my water due to the innacuracy of it.


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## des (Jul 30, 2011)

Thanks for the direction and advice.


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## des (Jul 30, 2011)

altcharacter said:


> You'll find out really quick with tanks under 10 gallons that it's not going to matter what your salinity is everyday due to evaporation. My salinity in my 6 gallon would be .024 in the morning and by the time I came home from work it might be .026. A refractometer would be nice if you could get one but a hydrometer would work for your setup due to how small it is even though they're not as accurate. I take 3-4 readings on my hydrometer when I change my water due to the innacuracy of it.


If evaporation causes a jump to .026, would you simply add distilled water or in my case treated tap water with prime and it should bring the level back to .024?


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## PACMAN (Mar 4, 2010)

des said:


> If evaporation causes a jump to .026, would you simply add distilled water or in my case treated tap water with prime and it should bring the level back to .024?


correct.

as far as the refractomemter vs hydrometer goes..... *ALWAYS GET A REFRACTOMETER. IT IS WORTH THE MONEY!* due to accuracy!


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## altcharacter (Jan 10, 2011)

Yep, R/O water is cheap. I get it from one of those kiosk thingies at the grocery store for a reasonable price. $2.75 for 5 gallons and if you're going with a smaller tank that would last you a month or so easily doing refills and water changes.

BA's charges 11 bucks now for their 5 gallon R/O water =(


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## PACMAN (Mar 4, 2010)

altcharacter said:


> Yep, R/O water is cheap. I get it from one of those kiosk thingies at the grocery store for a reasonable price. $2.75 for 5 gallons and if you're going with a smaller tank that would last you a month or so easily doing refills and water changes.
> 
> BA's charges 11 bucks now for their 5 gallon R/O water =(


I bought a RO unit for $130 and im sure I have made my money back from it. 1 year old and still pumping out 0ppm TDS. (140ppm coming into the unit)

50 gallons =$125 @BA pricing.


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## altcharacter (Jan 10, 2011)

Yep, I got my R/O unit off CL 2 weeks ago for 30 bucks and it works like a champ...no more grocery stores for me!!


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## mrobson (Mar 5, 2011)

refractometer and r/o water not tap FTW


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## Nightstar (Nov 26, 2011)

sig said:


> you can not compare two. Hydrometers are not accurate
> 
> http://www.aquariumsupplies.ca/salinity-refractometer-p-2582.html?osCsid=pf46rrqplltop5tatt4er3qae5


You are wrong. Here are some links.

http://www.advancedaquarist.com/2006/9/lines

http://www.wetwebmedia.com/ca/volume_3/cav3i4/hydrometers/Impressions.htm

My Original Seatest hydrometer gives repeatable results and is accurate. It has served me well for decades.


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## solarz (Aug 31, 2010)

mrobson said:


> refractometer and r/o water not tap FTW


I've always used tap water for my tank and it's served me well.


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## sig (Dec 13, 2010)

Nightstar said:


> You are wrong. Here are some links.
> 
> http://www.advancedaquarist.com/2006/9/lines
> 
> ...


It does not make sense to argue and you free to use what do you want. It did not work for me and for most of the reef keepers.

I hope you went first trough these articles before publishing.

"Conclusion
At this stage I am only presenting opinion. No statistics have been performed and I admit that the condition of the hydrometers is not something I could reproduce. It is my opinion after seeing these results that plastic hydrometers are perfectly acceptable for use in the hobby. I would say they are even acceptable for use in research. Their precision appears to be well within the range of projects I've seen conducted in laboratories. *Their accuracy is variable, but with a known (and easily found) correction factor these hydrometers perform quite well."*

"*In the strictest of senses, this value can never really be determined. It can only be approximated*."

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## mrobson (Mar 5, 2011)

Nightstar said:


> You are wrong. Here are some links.
> 
> http://www.advancedaquarist.com/2006/9/lines
> 
> ...


the 1st link test is flawed it provides no true base reading and the 2nd test only uses brand new hydrometers. No one is saying they dont work, just that refractometers are easier to use and more reliable. I own 2 hydrometers and 1 refractometer, i dont think i would ever go back to using hydrometers just for the ease of use. I got my refractometer for $30 with everything needed to calibrate for that price why wouldnt you get one.



solarz said:


> I've always used tap water for my tank and it's served me well.


Im not saying it wont work, but from what ive seen tanks using RO seem to be healthier. When i 1st set up my tank i used treated tap and ended up with a green hair algea outbreak, since switching to RO ive had no outbreaks and stable parameters. It could of been caused by by cycling but when you've spent a fair chunk to create your tank why cut corners to save a few bucks. The way i look at it is a car will run on cheap gas but it will run better on the good stuff.


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## sig (Dec 13, 2010)

solarz said:


> I've always used tap water for my tank and it's served me well.


For sure it works when you do not have enough biological load in the tank to produce phosphate on top of the phosphate in the tap water. It will start later with introducing more live in the tank.

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## des (Jul 30, 2011)

Thanks guys. 

I went with a Sybon refracto for it's simplicity. As some of you stated, it is easy to use. The Fluval Edge is only a 6 gallon tank with a small top opening so for me the hydrometer is not practical. 

Right now (temporary), I'm buying salt water in a jug from Big Al's. They said they will refill at $1 per gallon. It's not too bad considering I will only do about 1-2 gallon water change per week.

I recently learned that there's one shop that gives their customer free R/O water as a service. I bring in my empty jug and they will fill it. Not bad right? I would just need to buy salt and mix my own salt water.

I think I'm set. Again, thank you for everyone's take on this.


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## Nightstar (Nov 26, 2011)

mrobson said:


> the 1st link test is flawed it provides no true base reading and the 2nd test only uses brand new hydrometers. No one is saying they dont work, just that refractometers are easier to use and more reliable.


Sig said they dont work.



sig said:


> you can not compare two. Hydrometers are not accurate ]


I think both the studies linked demonstrate the accuracy of plastic swingarm hydrometers adequately regardless of perceived flaws in methodology. If you want to test your own hydrometer/refractometer you can prepare a reference solution and conduct the same test at home as I have done. I expect your results will be in line with the findings of the two linked studies.

Use whatever you are comfortable with, either will work if calibrated and operated properly.


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## azotemia (Jan 28, 2009)

How about a pinpoint monitor folks?


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## msobon (Dec 7, 2011)

One thing to add here, don't follow a refractometer as a holy grail without ensuring it's calibrated, I did that once, ended up having a tank that was1.035 due to a uncalibrated refractometer, rule of thumb each time before use try it on RO water, it should read zero or close to it.


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## mrobson (Mar 5, 2011)

azotemia said:


> How about a pinpoint monitor folks?


it would be nice but if a refractometer is too rich for their blood i dont see them springing for a pinpoint.



msobon said:


> One thing to add here, don't follow a refractometer as a holy grail without ensuring it's calibrated, I did that once, ended up having a tank that was1.035 due to a uncalibrated refractometer, rule of thumb each time before use try it on RO water, it should read zero or close to it.


i test once a month, mine came with a little bottle of pure water.


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## Yami (May 1, 2011)

i bet many people use dont use hydrometer correctly thats why it's not accurate. I personally buy the reputable brand of hydrometer from bigals, i rinsed it good each use because salt deposit can stay behind if you dont rinse it after each use. i always take the first reading then pour out the water and get the second reading to give a more accurate result. 

i have a refractometer needless to say i checked them side by side they had the same reading. If a product dont work, nobody will be buying it, the company will give up on the product.

but i must say a refractometer is well worth it, only $30 on ebay compared if $15 after tax for a new hydrometer. all refracto accuracy are the same dont buy the expensive brands.


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## BettaBeats (Jan 14, 2010)

refractometer. it's simple, its accurate, and a nice tool to show your friends


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