Refractometer vs. hydrometer

[jejton]

After reading some posts in another thread I wanted to throw this question out there. Has anyone actually tested swing arm hydrometers before parroting the statement that they are no good?

I read an article a while back - on RC I believe - where the author tested a few swing arm hydrometers, refractometers and an electronic monitor. Surprisingly, one of the ( calibrated ) swing arm hydrometers gave the most accurate reading, consistintly. Now as far as I know, from readings in and out of the hobby, having consistent water parameters is more important than having a certain parameter ( for many, but not all, qualities ). Living organisms are remarkably adaptable - if they weren't they would most all be extinct - and can adapt to a pH, SG, temp, etc. that is not their optimum or natural one. Yet in our hobby we spend so much time and money arguing if the perfect SG is 1.024 or 1.02553 or 1.02458, etc. Even if a swing arm hydrometer doesnt give me the accurate reading, as long as it is close to reality, and precise ( aka consistent ) it is as good as, and sometimes better than, anything more expensive. I say sometimes better because they dont need calibration and are more durable than electronic monitors or refractometers. The important thing though is to maintain them by soaking them in vineagar once in a while and using them correctly by shaking out bubbles. I wouldnt be surprised if most people's bad experiences with them have been due to user errors.

 

[PhoenixOne]

Funny you should mention the difference. I was told that the swing arm hydrometers can give false readings of sometimes .005 to .010 in some cases but no specific makes were mentioned.

 

[jejton]

http://www.wetwebmedia.com/ca/volume_3/cav3i4/hydrometers/Impressions.htm
http://www.advancedaquarist.com/issues/jan2002/chemistry.htm

 

[masterswimmer]

I was once part of a meeting of a group of about 25 reefers. We all decided to bring our refractometers and hydrometers (swing arm & floating). After testing all the various manual (not digital monitors) modes of measuring salinity we all left the meeting totally convinced that the swing arms had much too much variance and the refractometers were much more accurate.

When measuring salinity with swing arms you must make sure there are no bubbles 'stuck' to the swing arm, as this can hinder your reading. Water temperature also plays a big role in the accuracy of a swing arm.

Can you get consistent readings with swing arms? Probably yes, if you're diligent with taking your sample.

The ease of readings with a refractometer that is relatively inexpensive in this money pit of a hobby brings me to the conclusion that a refractometer is the way to go.

swimmer

 

[jejton]

You tested hydrometers against refractometers but did you test either against a calibrated standard? If not, for all you know, unlikely as it might be, the refractometers were precise but not accurate either. The reason I bring this up is because this hobby, as you state, is a money pit but unfortunately money is often needlessly spent where it can be better spent on things like livestock.

 

[fritz]

Agreed,
Mike Slamajama aka Mountainreef and I both tested our swing arms with a refractometer and found that the swing arms were dead on accurate. I've also seen 5 or 6 of the same brand hydrometer give different readings of the same water. Bubbles as Russ stated and crud built up on the arm, salt deposits etc leave a lot of room for variation.

Floating glass hydrometers however I think are pretty dead on.

 

[Teddy]

Yea I agree with Swimmer

When I first started this hobby, I bought a swing arm (hydrometer). It told me that my salinity was around 1.025 or 1.026. Used it for like 2 month. Washed it after every use, tap it to make sure there was no bubble inside during testing.

One day I decided to take my water to LFS to test parameter, he told me that salinity was at 1.020(he used refractometer ). Wow, that is shocker. Of course I didn't have one of those. So I bought one from ebay. When it came, LFS was right, salinity at 1.020..

I also believe that when you quaratine a fish and need go to hyposalinity to treat ich, refractometer will give you a better reading than using a swing arm..

So I do believe that refractometer is better than a hydrometer...just my 2 cents...

 

[PhoenixOne]

Lol...guess what I'm buying next? Don't need to tell me twice.

 

[Pinkheine]

Just a question... by tested what do you mean? Like for example has anyone ever done a study using say 100 swing arm hydrometers and 100 refractometers and documented the results... to see which is better/more accurate?

I can only speak from our personal experience of nine years with saltwater tanks. In the beginning we used a hydrometer because it was cheap and we figured it would be accurate enough. What we would do was buy the hydrometer and test our water, then take water to the LFS and let them test it with their refractometer... and note the difference (there was always a difference) then we would add or deduct that to our hydrometer readings at home and get the actual salinity.

But in the amount of money we spent in the first few years on hydrometers (oops it dropped and broke etc.) we should have bought the refractometer from the beginning. We waited until the LFS had a sale on them and picked one up. It is by far much easier and quicker to test and in our experience has been more accurate than the many hydrometers we have used in the past.

 

[rgun2515]

I have both and test my water with both every time. Readings have always been the same on both, the Refractometer and the Hydrometer.

These are the devices I have and use.

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=4945

and

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=9957

 

[tosiek]

Its not so much that the swing arms always give bad readings, its that you will have no way of knowing its off, and a salinity swing can kill things in your tank. If they were always giving bad readings im sure they wouldn;t be sold. They are accurate but as long as you give them proper attention when cleaning/reading/ect. Always take more than one test when your testing water, always check it against a constant somehow and so on.

Ive used a swing arm for a long time, same one too. Never had a problem, always got accurate results. I tested it occasionally with tank water from a friend of mine who used a refracto. Switched it out when my livestock started acting up and found out my salinity was way high. I got a refractometer and stuck with that. Just too much you can't controll or check if they are off. You have to switch them out every few months because of the crud build up you won't 100% clean. And ive read that sometimes you get a bad swing arm due to bad shipping/ect.

You can calibrate the refractometer but you can't calibrate or adjust the swing arm. And if your gonna have to switch up swing arms every few months it comes to half the price of a refractometer, which u can calibrate.
If your in the hobby for more than a year and a half im guaranteeing you that you will spend as much in swing arms as you would a refractometer. So, the price difference and trying to save a buck methodology is down the drain =0P It all depends on how much you want out of the hobby and how long your gonna be in it.

Fitz how many different hydrometers and refractometers did you test? 1 or 2 or more? and how old were each. What brands?

And if you buy a crappy refractometer im sure your getting what you pay for, and the same goes with hydrometers. Im sure the reason the online marine stores only carry 1 or 2 brands is because of the send backs on broke refracto's.

 

[tosiek]

Pinkhein, Its not that they are not accurate when you get them, for the most part they are dead on. There is no way to calibrate the swing arms after usage. And salt creep/ect is what does them in. You won't know it.

 

[rgun2515]

And if you buy a crappy refractometer im sure your getting what you pay for, and the same goes with hydrometers. Im sure the reason the online marine stores only carry 1 or 2 brands is because of the send backs on broke refracto's.

What would you consider a good refractometer.

 

[tommy818]

agree with swimmer

 

[cali_reef]

People need not to be in the hobby if they can't or don't want to spend $35-$40 for a refractometer. A typical fish or a small coral cost as much.
My refractometer is about 6 years old, will your fish or coral last this long with a swing arm you can't be sure its accuracy?

 

[Solace Aquatics LLC]

People need not to be in the hobby if they can't or don't want to spend $35-$40 for a refractometer. A typical fish or a small coral cost as much.
My refractometer is about 6 years old, will your fish or coral last this long with a swing arm you can't be sure its accuracy?

Precisely

 

[KathyC]

I don't know that you need to think past the point that refractometers can be calibrated.
Probably about the best, inexpensive, important items in the hobby. Why penny pinch?

 

[jejton]

You can calibrate the refractometer but you can't calibrate or adjust the swing arm. And if your gonna have to switch up swing arms every few months it comes to half the price of a refractometer, which u can calibrate.

Good points but one correction - you can calibrate a swing arm - just like calibrating any other measuring device. It just needs to be consistent. You could probably adjust them if you did a little research but I doubt its worth the effort.

 

[jejton]

Cali and Kathy - My reasoning behind this thread was not about penny pinching. It was to ask if there is any rational or evidence behind the dogma ' refractometers only. ' Way too often people repeat things that they have heard as though its fact, without having actually done any research into it. Happens with everything, not just this hobby.

In medical school, the new buzzword is EBM - evidence based medicine. No more doing things because your grandpappy did it and you think it works. Insurance won't pay for it and malpractice lawyers will skin you alive.

The same thing should go for this hobby. I dont care if something costs $5. If it doesnt do what its supposed to, or there is no REAL need for it, I'd rather keep my $5 for another gallon of gas or some TP. OTOH, if it costs $500 but is necessary, then I'll buy it ( assuming TP is already taken care of for the month ).

 

[tommy818]

the problem in this hobby is once a trend starts everone tends to follow and it makes the newbies get more mislead information some hobbiest are making things more and more complicated all this unessecery equipment controllers probes ect.and other gadgets.they should concentrate on maintaining good water quality keep things as simple as possible.