Accurate salinity measurement

Discussion in 'General Discussions and Advice' started by Furbz, 20 Sep 2013.

  1. Furbz

    Furbz

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    So,

    for a long while i have been using a floating glass salinity meter.
    i have 2 of these (the normal ones you buy from pet stores)

    recently i was given a ATC refractometer :)

    now get this! using both my floating glass salinity meters i measured my tanks water to be 1.024.

    then using the calibrated refractometer it confirmed my salinity was actually sitting at around 1.028!

    Jinne!
    so both the floating glass salinity meters were miles out!!

    i did another test on my QT tank.
    floating glass salinity meter read 1.010
    refractometer 1.014

    i have since lowered my salinty and my fish are looking far happier for it!
     
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  3. 459b

    459b Moderator MASA Contributor

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    I think its a myth that a refractometer is automatically the more accurate instrument.
    Compared to the refracto's that are used in industries, ours are far from top quality. Alot of applications still choose float hydrometers over refractometers.
     
  4. Reefhead

    Reefhead

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    Everyone rights off the poor hydrometers but if you get the right one they can actually be more accurate then refractometers. The problem is you don't find that grade hydrometer in the marine trade easily, they more in the chemical industry.
     
  5. Reefhead

    Reefhead

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    Agreed
     
  6. Furbz

    Furbz Thread Starter

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    thanks for the feedback guys

    i agree that my 2 hydrometers are not top quality.

    my refractometer is a D+D. so i'm hoping it is more reliable than my no name hydrometers?
     
  7. Furbz

    Furbz Thread Starter

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    on that note

    does anyone possess a top quality hydrometer or top quality refractometer?
    if you do please share your experience??
     
  8. Reefhead

    Reefhead

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    It should def be
    I have always wondered why though that they don't make a good quality hydrometer for the marine trade, would be the same sort of price as a recfractometer but IMO far more accurate.
     
  9. Reefhead

    Reefhead

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    Have both and I prefer the hydrometer
     
  10. Nemos Janitor

    Nemos Janitor

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    Guys I have been over this subject many times. Both the glass salinity meter/ hydrometer and the refractometer are most likely correct. Discrepancies in readings are normally due to temperature and interpretation of the reading. As stated before, most refractometers indicate a SG at 20c whilst a hydrometer indicates a SG @ 25c. Hydrometers are extremely fussy with temperature. Check the calibration temp on the instrument then test the Sg at that temp.
     
  11. MistaOrange

    MistaOrange

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    Agreed...:thumbup:
     
  12. viper357

    viper357 Admin MASA Contributor

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    I have one of the bigger hydrometers, made by Tropic Marin, it is a lot more accurate than a refractometer because it reads in smaller increments/scale, but it was near enough as makes no difference when compared with my Hong Kong refractometer.:thumbup: Although since it proved my refractometer accurate enough it has since been banished to the garage because quite frankly, it's a pain to use. :p

    Here's a pic comparing to a dinky little hydrometer

    [​IMG]
     
  13. Handy

    Handy

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    I use all both and they all give different readings. I have a profilux 3 and it gives me the worst reading of them all, re calibrated and still incorrect reading, so i take an average of all three
     
  14. pkc

    pkc

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    I use a tiny plastic specific gravity tester that my brother gave me in 1980 and still use it as my only salinity tester.
    I have tested it against refractometers over the years and it was always with in half a point with each comparison.
    I don’t like the floating hydrometer type described in this thread, that’s from others experiences with them, I have never used one.
     
  15. CharlieB

    CharlieB

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    My Red Sea hydrometer was reading 1.025 and then when I got my refractometer it showed 1.030! Might explain why my corals were dying. Which one is right who knows but the fact I don't have to worry about bubbles and temp and sticking and that I can calibrate my refractometer I prefer it and trust it more. Can also get a more accurate reading off it. But whether that reading is correct or not after threads like this who knows haha. I just read my fish and corals more:)
     
  16. pkc

    pkc

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    Right on, there are several life forms I use for water quality indicators.
    Far more reliable then testing!
     
  17. archiecrain

    archiecrain

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    I use a Tropic Marine Hydrometer. Its so easy to get an accurate reading, but its a pain to use as its sooooo delicate.
     
  18. VicZA

    VicZA

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    anyone know where to get an electronic one ? I would be looking for one that can give a 0-10VDC or 4-20mA signal output ....
     
  19. Ridwaan

    Ridwaan

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    I have also changed to the Tropic Marin Hydrometer...
    haven't used a refractometer in a very long time...
     
  20. shan

    shan

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    I have been using my Tropic Marine Hydrometer since 2007 and it has not given me any issues yet. Its not that bad to use. Just turn off all power and float the thing. Takes a few minutes.

    But I do worry about it breaking.
     
  21. KeeganP

    KeeganP

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    Last edited by a moderator: 20 Sep 2013
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