# Whats wrong with my Hydrometer????



## chimera779 (Jan 7, 2011)

I have hydrometer and its been saying my specific gravity levels are 1.025 Which is fine with me so i left it at that for a week or 2 and now i borrowed a refractometer from a friend and it read 1.018!!! So this whole time i been thinking the hydrometer is correct. But how could the refractometer be wrong?? So which one is more correct i need help soon thanks!


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## cbirk (Feb 5, 2010)

refractometers are more accurate. hydrometers are subject to mis reading, and errors that can arise such as having bubbles in the swing arm. What exactly can go wrong is dependent on the kind of hydrometer you have. Thats about the limit to my knowledge however, so hopefully someone else can go a little more indepth.


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## reefsahoy (Jul 16, 2010)

chimera779 said:


> I have hydrometer and its been saying my specific gravity levels are 1.025 Which is fine with me so i left it at that for a week or 2 and now i borrowed a refractometer from a friend and it read 1.018!!! So this whole time i been thinking the hydrometer is correct. But how could the refractometer be wrong?? So which one is more correct i need help soon thanks!



optical refractrometers are more accurate than swing arm hydrometerss but thats no to say the swing arm isn't any good!. To use the swing arm make sure there are no tiny (and i mean tiny, so look closely) bubbles on the swing arm. You also need to clean it with fresh water after every use otherwise salt will eventually stick to the arm. When i use to use a swing arm i would use a tooth pick and tap/scrape the arm to get rid of any tiny bubbles on the arm when measuring the salinity. Usually after doing this you'll record a different measurement before and after that process. however, the best way to measure salinity is to use the optical version but make sure you clean the glass with fresh water otherwise salt buildup will occur there too


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## chimera779 (Jan 7, 2011)

okayy yeah the thing i had my hydrometer for a few years and i never knew to like clean it off and i didn't know there were bubbles on it either...so i must of been mis reading that thing for a long time luckly i just started my reef tank and ill keep using the refractometer cause i even used a newer hydrometer and it still read what above the charts..but i cleaned the glass of the refractometer n used it n it said 1.022 instead of the hydrometer which read 1.026 so ill have to invest in buying my own soon thanks


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## cbirk (Feb 5, 2010)

yeah, from what I have read, depending on what hydrometer you have, it can be off by up to .06


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## chimera779 (Jan 7, 2011)

yeah like thats insane!!! i have a reef tank now and i cant be wronggg otherwise i heard you can have major problems down the line if u dont keep your specific gravity levels between 1.023 and 1.025


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## njudson (May 21, 2009)

just for the sake of information. Refractometers can be wrong too, they tend to drift and need to be re calibrated periodically


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