Bad Hydrometers
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Nabber86
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The problem with a cheap refracto is that you can not assess the accuracy or precision because that information is not supplied by the manufacturer (somewhere in Hung Ko province, I suspect). The calibration simply is not certified or documented in any way, shape, or form.
A good hydrometer comes with a calibration that is certified and traceable. The accuracy and precision are stated for each instrument.
integlikewhoa
New member
But if you do your own calibration with a premixed solution. Will they ok or still far off?
Before everybody knocks on the $5 I.O. hydrometer, remember that you have to take your sample, then tap on the hydrometer (with spoon) to loosen and dislodge any microbubbles. I have seen so many people take a sample, set it down, and just stare at the reading. If you dont tap the bubbles out, they stick to the arm and throw the reading off by about .02-05. For safety measures, I use 2 of them and 1 float, thermeter which also gauges salinity. For only $5, thier pretty accurate in my experience.
outta names
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Bigbert- I wasn't trying to knock the IO hydrometer just sharing my experience with everyone. I had no clue that for 6 months my salinity was @ 1.18-19 b/c my IO said it was @ 1.24 and as a result every shrimp and lots of snails died. My purple coraline also would not grow and I hope this is the reason why b/c all my other parameters are o.k.
Thanks to everyone for your info.
Thanks to everyone for your info.
If you calibrate a cheap refractometer according the directions, it should work quite well. Actually, they seem to work reasonably well when calibrated with RO-DI water. The moderator in the chemistry forum did a study of a bunch of samples brought by aquarists to a club meeting, and a lot of other people, including me, have tested them.
The problem with the floating hydrometers is you'll need to do temperature conversions, most likely, since the water sample will not be at the reference temperature for the hydrometer. Or you could calibrate them with the standards from the article, but then they would have the same accuracy as the refractometer, most likely.
The problem with the floating hydrometers is you'll need to do temperature conversions, most likely, since the water sample will not be at the reference temperature for the hydrometer. Or you could calibrate them with the standards from the article, but then they would have the same accuracy as the refractometer, most likely.
I agree.
Check the chemistry forum for a homemade calibration solution.
When I started I was lucky enough to get my swing arm hydrometer from an experience reefer and good friend. He said "it reads about .004 low"
I followed this and when my refractometer came, sure enough he was correct.
Plus with a refractometer checking salinity is a 15 second deal....drip, look, done.
Check the chemistry forum for a homemade calibration solution.
When I started I was lucky enough to get my swing arm hydrometer from an experience reefer and good friend. He said "it reads about .004 low"
I followed this and when my refractometer came, sure enough he was correct.
Plus with a refractometer checking salinity is a 15 second deal....drip, look, done.
integlikewhoa
New member
a lot of problems with the swing arms comes form not cleaning them and servicing them properly.
Nabber86
New member
Good point.
I think the real take home message here is that the key to getting good salinity measurements, no matter what instrament you are using, is to check your readings against a known standard solution. And do it often, or at least enough times that you are comfortable that it is giving you accurate readings.
The Reefer91
New member
what about this? if you wanted to go all out(relativley)
http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=4486&N=2004+113762
http://www.drsfostersmith.com/Product/Prod_Display.cfm?pcatid=4486&N=2004+113762
outta names
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I would have to agree with you nabber96, with that being said is there a solution out there that we can buy that is pre-set at a certain salinity that we could use as a reference to determine if our salinity meters are correct?
outta names
New member
Does anybody know?
Nabber86
New member
Nabber86
New member
To reference check a refractometer, you could use this (a little pricey, though):
https://www1.fishersci.com/Coupon?gid=196870&cid=1328
or maybe this if you have a conductivity based meter:
https://www1.fishersci.com/Coupon?cid=1336&gid=313043
Otherwise, use a good gram scale and a volumetric flask to mix your own standards
outta names
New member
Thanks nabber, just out of my price range :eek1:
Either of the two conductivity meters shown, the JBJ or the PinPoint, should do the job. My PinPoint is working well for me. Both of these product should come with a calibration solution. The PinPoint comes with a 53 ms standard, which is perfect, and you could use it with the JBJ, although it probably has its own calibration points.
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