question about a hydrometer

[semoluv]

bought a new hydrometer....says to rinse it out with fresh water before testing. when i do, it shows the specific gravity of the tap water at <1.032. in other words, its saying the fresh water is off the scale. then, when i test the saltwater that i have just mixed, it gives me another off the scale reading. however, when testing the aquarium water, i get a 1.022 reading.
what am i doing wrong?

 

[alix2.0]

Originally Posted by semoluv
what am i doing wrong?

youre using a hydrometer... i would say spend the extra $ and get a refractometer. much more accurate.

 

[howardj]

well.. wait..
are there tinny bubbles on the needle?
That would cause it to raise to 1.032

 

[semoluv]

no, i did the "tap" thing to release the bubbles...it is clear, and i'm still getting this 1.032. strange, because like i said, it measures the tank water correctly....

 

[marka1620]

Get a refractometer............worth the money. I also started with the hydrometer and it was a waste of $15.

 

[swfishfan]

you can get a really nice refracometer on that big website were you bid, for about 30 something, they come with everything included too. but yeah your going to get this alot with this post hydrometer's are a waste of cash....

 

[beth]

Swing arm hydrometers are so inaccurate as to be dangerous. Cut your loss and throw it out. Get a refractometer.

 

[geoj]

It would be nice if people with strong opinions would do us the kind act of explaining why they have their opinion.

 

[lexluethar]

Hydrometers are crap - I will explain for you GeoJ.
I first bought a hydrometer like 95% of the hobbiests and everything seemed fine. My fish were happy and everything was honky-dory. The only problem. Every time I tested my SG it would be a different reading. I sometimes got things like 1.018 and the next day (same time of day) I would get 1.027. Long story short I RARELY got the same reading and my temperature and water level never changed during this "test phase".
I bought a refractometer and tested both for about two week to see what all the hype was about. Well my first test showed that with the ref. my SG was 1.018 and with the hydr. it was 1.025 (where i thought i wanted it). I tested over a few weeks time and the ref. CONTINUALLY GAVE THE SAME RESULT - with the exception of when the water level was lower b/c of evaporation my SG was higher. Needless to say the hydrometer was off and different every time.
So what does this mean? Using the raw numbers AT BEST the difference was hydr. 1.025 and the true measurement was 1.018. So that is roughly a 24% difference in the swing arm and the true SG.
Use what you want, use what fits your budget. But if you can't afford a 30 dollar piece of equipment IMO you have your priorities mixed up.

 

[geoj]

Thanks Lex I will have to go out and get one. Any one else with some insight.

 

[gmann1139]

Over time, a refractometer is going to be the second cheapest piece of testing equipment you own, after the thermometer.
You can get a cheap one for $40. I just helped a buddy set up a 12 gallon, and even with lending him my copper and phosphate testing supplies, he still spent more than $60 for 20 test kits of everything.
If he tests weekly, plus 8 'emergency' tests a year, that's $180 a year for 5 different tests (amm, nitri,nitra,pH,alk).
That refractometer doesn't sound so bad anymore, does it?

 

[notsonoob]

Originally Posted by semoluv
bought a new hydrometer....says to rinse it out with fresh water before testing. when i do, it shows the specific gravity of the tap water at <1.032. in other words, its saying the fresh water is off the scale. then, when i test the saltwater that i have just mixed, it gives me another off the scale reading. however, when testing the aquarium water, i get a 1.022 reading.
what am i doing wrong?

Get yourself a 20 pound sledge...
SMASH
SMASH
SMASH...
The same thing happened to me. Get a refractameter

 

[stdreb27]

Originally Posted by GeoJ
It would be nice if people with strong opinions would do us the kind act of explaining why they have their opinion.
lol, I agree, hydrometers aren't accurate because of poor manufacturing, and a wide range of things that can effect the reading. A refractometer isn't suspect to alot of those problems. It would take forever to explain all the different reasons why. But it boils down to the margin of error to manufacture something that will float at certain specific gravity is to small to cheaply mass produce. You will find if you choose to look glass ones that are quite accurate, but those are more expensive than refractometers for marginal if not equal performance, so most of us use and reccomend them.

 

[calvertbill]

Originally Posted by alix2.0
youre using a hydrometer... i would say spend the extra $ and get a refractometer. much more accurate.
Ditto!

 

[peef]

Now I am going to let you in on a little secret that nobody has told you yet.......ssssshhhhhh come 'ere
*whisper* get a refractometer.....sssshhhhhhhhh don't tell anyone........
heh hehh heh heh

 

[xdave]

Ahhh baloney! Nothing wrong with hydrometers, yours is just bad.
According to tests done by Adam Blundell, M.Sc. "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."
(Adam Blundell M.S. works in Marine Ecology, and in Pathology for the University of Utah. He is also Director of The Aquatic & Terrestrial Research Team, a group which utilizes research projects to bring together hobbyists and scientists. While not in the lab he is the former president of one of the Nation's largest hobbyist clubs, the Wasatch Marine Aquarium Society. Adam has earned a BS in Marine Biology and an MS in the Natural Resource and Health fields.)
He isn't the only one that finds cheap plastic hydrometers very accurate. Another hydrometer test

 

[jay&beck]

Funny you should ask, I was having the same problem and after doing some research, I decided to purchase a refractometer off that big site you bid on. I got mine for $25. Just make sure it says RHS and ATC. Mine works great best thing I could have done.

 

[lexluethar]

You cannot conduct a VALID test one time and tell my that the results are statistically accurate - because they are not. Conduct that same test for 7 - 14 days with all hydrometers and THEN you can make a case.

 

[lion_crazz]

Originally Posted by Beth
Swing arm hydrometers are so inaccurate as to be dangerous. Cut your loss and throw it out. Get a refractometer.
I fully agree. Hydrometers should not even be sold.

 

[m0nk]

The thing about hydrometers is that they measure specific gravity, not salinity. Basically, ANY particulates in your water that could change the gravity of the water will throw off your readings, which could end up being rather high compared to actual salinity. My hydrometer seems to give anywhere from 0 - .003 points off from my refractometer readings, and it's never consistent. Now, let's say you keep your SG at 1.022 and have inverts. A deviation of - .003 would bring your salinity too low and potentially kill your inverts.
Here's another thing to think about. This isn't the only hobby where some hobbyists use a hydrometer and others use a refractometer. I also have made wine in the past, and even worked at a winery. As a hobbyist I used a hydrometer to test sugar levels prior to making the wine, which would give an approximation of alcohol levels, but working in a winery I had to use a refractometer for accuracy. The reason there is that you need to be sure that your grapes are ripe enough to give you a good alcohol content while keeping at a certain acidity level. If you have that reading .003 points off your wine could turn out terrible and no one will drink it. That's a big problem when you're harvesting 13,000 lbs of grapes for that year's batch of Cabernet Sauvignon.