I thought this was interesting

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nereef

Guest
*Link Removed*
*Please copy and paste the article with the author's name instead of posting the link*
 

miaheatlvr

Active Member
Originally Posted by NEreef
*Link Removed*
VERY INTERESTING INDEED, so what are you telling me, I blew $100 on my refractometer for nothing?? LOL, Listen people have been using these plastic hydrometers for DECADES, People have had successful aquariums before us using plastic hydrometers and people will have successful aquariums for decades after us USING plastic hydrometers!
 
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nereef

Guest
i'm curious to see how he will obtain used hydrometers, or how he will condition new ones to be old.
 
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nereef

Guest
well, that was a good thread. why was that deleted? i can't copy and paste the article because it has too many characters.
*Sorry, but the reason why the link was deleted was because it contains links to competitor sites*
 

whitey_028

Member
Originally Posted by NEreef
well, that was a good thread. why was that deleted? i can't copy and paste the article because it has too many characters.
ive had to copy and paste in 3 seperate post t get large articles like that....
 
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nereef

Guest
By Steven Pro
I am going to take a slight departure from my regular Impressions column this month. Instead of merely describing what I think about a particular type of equipment and the brands/models available, I will instead be detailing some product testing that I conducted. While I believe my standard Impressions column is worthwhile, it is inherently based upon anecdote and experience. In some instances, like power filters for example, I have handled hundreds of each brand and model. But with protein skimmers, in some cases I have only used three or four of some models. This limited experience can shade my opinion because of the flaws or alternatively fine performance of those units in that small sample. If I have only used a few of a product and all those were fine, it would give me the opinion that this brand was reliable whether or not that was the case. And of course, the opposite could be true. I could use a few of one brand and discover those were defective for some reason, but that may not necessarily be representative of the entire line.
While it is a commonly held belief that the standard box-style, swing-arm hydrometers are inaccurate, like so much else in this hobby, this belief is based solely on anecdotal evidence and experience and not based upon scientific study. After the release of the new and improved Marineland Labs/Aquarium Systems hydrometer, I decided to change that. I wanted to put this product through a series of tests to evaluate its accuracy and consistency when brand new, to reevaluate both after extended use and in some cases, a bit of abuse. I was particularly curious if the product was inaccurate and imprecise as manufactured or if they became inaccurate and/or imprecise only after use.
The first thing I should probably do is define some terms. (The following terms and definitions come from Beckwith, Buck, & Marangoni, 1982.) There is the true or actual value of something. In the strictest of senses, this value can never really be determined. It can only be approximated. There is also accuracy, which is the maximum amount by which the result is different from the true value. And finally, there is precision. Precision is how close the results are to each other. An extreme example of precision versus accuracy was given in the text book for illustration. “If all clocks in a jewelry store are set at 8:20 but are not running, the indicated values show precision but are accurate only twice per day". So, an instrument (or group of instruments) can be precise, consistently measuring the same value, but not necessarily accurate if those values are always incorrect. Additionally, an instrument can be occasionally accurate, but not necessarily precise if it gives wildly varying results. In the worst case, an instrument can be both wildly inaccurate and inconsistent, therefore neither accurate nor precise. Ideally, one would want an accurate and precise instrument, but could settle for a precise one if the error (the actual difference between the true and measured result) was known.
The design of the Aquarium Systems hydrometer has changed over the years, though the basic design is the same. The most recent design (far right) is the one tested for this article. Photo by Steven Pro
 
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nereef

Guest
Before I could begin my experiment, I had to obtain a sample group of hydrometers. I could have just purchased a case of them through one of my wholesalers, but this would have resulted in me likely getting just one batch or lot. This would not necessarily tell me how well this product would work, just how well this particular group did. In an effort to lessen the likelihood of obtaining a single batch, I enlisted the help of friends and acquaintances from all over the country to purchase hydrometers off the shelf and ship them to me in their original packaging. Additionally, I picked up a few hydrometers in my own travels around the country. Below is a listing of all the locales I was able to obtain a hydrometer from:
Pittsburgh, Pennsylvania
Cleveland, Ohio
Atlanta, Georgia
Dallas-Fort Worth, Texas
Salt Lake City, Utah
Los Angeles, California
East Lansing, Michigan
Ithica, New York
Las Vegas, Nevada
Denver, Colorado
Orlando, Florida
Sacramento, California
To satisfy my own curiosity, I labeled all of these locations on a map of the United States that I had laying around. From the image, one can see that while there is a definite Northeast concentration, most of the hydrometers came from all over the US.
Phase One - Initial Testing:
I first had to test these twelve hydrometers to determine if they were consistent and accurate right out of the box. This was the most critical part of my experiment. If they did not ‘pass’ this first round of testing, subsequent phases would be unnecessary and my article would be awfully short.
Fresh water was purified by an Aquatechnik separate stage, two resin deionization unit. Tropic Marin Pro Reef salt mix was added to obtain a salinity of 36 ppt or approximately 1.027 specific gravity at 78*F according to a Sybon Opticon Series FG100sa refractometer with automatic temperature compensation. The refractometer was calibrated prior to taking measurements with a reference sample of pure water (< 18 M&#8486;-cm and 0 ± 0.01 ppt). Initial water quality was checked on the batch mix of saltwater with Salifert test kits and was recorded as follows:
pH 8.2
Calcium 400 ppm
Alkalinity 3.0 meq/l
Ammonia 0 ppm
Nitrite 0 ppm
Nitrate 0 ppm
Phosphate 0 ppm
I then checked the specific density of the same seawater mix with the various hydrometers I had obtained. The values are recorded in the chart below.
Hydrometers
Measured Value (Specific Gravity)
Measured Value (Parts Per Thousands)
1
1.027
36
2
1.027
36
3
1.027
36
4
1.027
36
5
1.027
36
6
1.027
36
7
1.027
36
8
1.027
36
9
1.027
36
10
1.027
36
11
1.027
36
12
1.027
36
As one can see from the above chart, all the hydrometers were both precise and accurate. I must admit that I found this to be a bit of a shock! To see such a high degree of accuracy and precision out of a $15 cheap piece of plastic astonished me. Furthermore, I had heard all the stories and seen it for myself that hydrometers tend to be inaccurate after some use. So, is this level of accuracy and precision due to the “new & improved” style hydrometers’ design or are all plastic hydrometers good right out of the box, but tend to drift with use? This will be the subject of the next round of testing.
References:
Beckwith, Buck, & Marangoni. 1982. Mechanical Measurements. 3rd Edition. Addison-Wesley Publishing Company. Reading, Massachusetts. Pages 262-263.
 

laddy

Active Member
Sometimes I think salinity/SG is blown a little out of proportion in the hobby......the difference between 1.020 and 1.026 is significant, however, the difference between 1.024 and 1.025 is not. I think if you're not running too intricate systems a plastic hydromtere is probably a good bet, and a refractometer is the last purchase you should make........and for the record, I have a refractometer and use it often.
 
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nereef

Guest
keep in mind Steven Pro's reference, mechanical measurements. he used the hydrometers exactly how they are supposed to be used, which i'm sure a lot of us don't use them correctly.
 

laddy

Active Member
Originally Posted by NEreef
keep in mind Steven Pro's reference, mechanical measurements. he used the hydrometers exactly how they are supposed to be used, which i'm sure a lot of us don't use them correctly.
Very true. I don't think a lot of people in this hobby use things correctly. IMHO.
 

xdave

Active Member
I've found over the years that most of these hydrometer types inaccuracies could be attributed to user error. You must tap it to get the bubbles off of the arm. People mix up the SW with cold water and measure it, leave it overnight in a bucket with a heater, then get a completely different reading.
Whenever somebody hits their thumb with a hammer, they always blame the hammer.
 

shogun323

Active Member
Originally Posted by xDave
I've found over the years that most of these hydrometer types inaccuracies could be attributed to user error. You must tap it to get the bubbles off of the arm. People mix up the SW with cold water and measure it, leave it overnight in a bucket with a heater, then get a completely different reading.
Whenever somebody hits their thumb with a hammer, they always blame the hammer.

Great point Dave.
 
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nereef

Guest
well said, dave. however, we still can't necesarily assume that hydrometers are as accurate or as precise as refractometers based only on this one test using new hydrometers of one brand.
 

ninjamini

Active Member
Originally Posted by NEreef
keep in mind Steven Pro's reference, mechanical measurements. he used the hydrometers exactly how they are supposed to be used, which i'm sure a lot of us don't use them correctly.
What is the proper way to use a hydrometer?
 

emmitt2

Member
I dont know about anyone else but my hydrometer NEVER gave the same reading twice, no matter what i did. I wouldn't trade my refractometer for every new hydrometer in the world regardless of what Steven writes.
I've read enough of his articles and posts elsewhere to know that if you posted in his forum that hydros are very accurate, he would probably get all high and mighty and tell you that is wrong. I've seen him post things that directly contradict what he writes in his articles.
 
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nereef

Guest
Originally Posted by ninjamini
What is the proper way to use a hydrometer?
1. they are calibrated to a certain temperature, so in order to get an accurate reading, the water you are measuring has to be close to that.
2. they need to be rinsed with fresh water before each new use. otherwise the saltwater in them evaporates, leaving salt crystals and skewing your measurement upward.
3. they need to be free of air bubbles. you can flick the bubbles out if you do it correctly.
 
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