Refractometer?

Discussion in 'New To Reefing' started by Adam_w, Aug 23, 2016.

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  1. Adam_w

    Adam_w Member

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    Hey everyone,

    Prepare for long winded question!

    Bit new around here but my tanks been up about a year, when i first got it the shop sold me both a little thermometre which floats to tell you the salinity. Also got another thing for salinity where you fill it with water and a little arm moves to tell you the amount (not sure whats its called)

    Apparently this has been a huge oversight on my part and I should be using a refractometre - just wondering if there's any recommendations on these? i also read they need to be calibrated after use??

    Bit lost but there's some on ebay for around $30 and i figure they're all relatively the same aside it the more expensive ones being branded

    what would be anyones thoughts on this?

    Thanks :)
  2. Franklin Dattein

    Franklin Dattein Member

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    You are in the right path. Throw the densimeters in the buy and get yourself a refractometer.

    I've always used cheap (~$30) refractometers and they do a good job. For piece of mind, also grab a refractometer calibration solution ($15) from you LFS or store NSW in a bottle and use as calibration reference.
  3. Adam_w

    Adam_w Member

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    Alright I'll pick one up then :)

    How does the calibration work with NSW? Does it just have to look the same?

    Hoping there's some good instructions with these things haha

    Thanks!
  4. A Barnes

    A Barnes Member

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    NSW can change in Salinity, for example QLD and the GBR sit at around 1.026, where VIC is at around 1.028. I'd be using a calibration solution that tells you what specific gravity your refractometer should read, I'd also make sure the one purchased can be calibrated. I've seen a few cheaper units that are set and cannot be adjusted at all. I think I picked up mine from my LFS for around $45, not branded, but fully focusable and adjustable.
  5. MagicJ

    MagicJ Moderator

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    Once you get one you will wonder why you didn't get one 12 months ago :)

    Everything you ever wanted to know about refractometers - http://reefkeeping.com/issues/2006-12/rhf/

    Welcome to The Reefuge @Adam_w.
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  6. Sean81

    Sean81 Member

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  7. macca_75

    macca_75 Member

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    welcome @Adam_w

    As others have mentioned. For our purposes calibrated off RO to 0.00 is fine for our purposes (do we really care if it's 1.026, 1.027 or 1.028 or do we care more that it remains stable)? If you MUST have an accurate measurement try and calibrate it as close to what you are measuring as possible.

    The little "swinging arm thing" is a swing arm hydrometer - pretty much usless.

    $30 on a refractometer will be a great investment. Try and get one that has ATC (Automatic Temperature Compensation) and more importantly can be calibrated - I think most units on the market are like this anyway.

    Oh - and @MagicJ link to the RHF article - perfect. Often good to understand the how and why, not just the what.
  8. Adam_w

    Adam_w Member

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    Sweet thanks for all the info guys, I've ordered one off ebay now says its got ATC and can be calibrated so fingers crossed. I think I'll use RO water to calibrate at the start and maybe when it warms up ill go to the beach and see how close it is?

    I'll read through those articles to big fan of knowing the how's and why's behind stuff
  9. IJG3145

    IJG3145 Member

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    I too use cheap ebay ones and just check them occasionally. BEWARE though, you need one designed for testing sea water - not salt water and not brine, they are all different refractometers. Some ebay sellers are even selling sugar refractometers as suitable for aquariums - I got caught and had to force a refund through Paypal..

    Salt water and brine ones are mostly used in food manufacturing, at MG we tested the salt solution vat salinity (goes into butter etc) and they give very different results to one designed for sea water.
  10. IJG3145

    IJG3145 Member

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    You won't get an accurate reading using RO, just go to the beach and get some sea water if you can.
  11. macca_75

    macca_75 Member

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    Worst advice ever

    Calibrating off an unknown.

    Calibrating of RO (known to be 0.00) will give a far more accurate reading. Calibrating of a DIY or purchased solution at or nearer to your target is better, but RO will suffice.

    If you use sea water as your calibration standard, what is the value? Answer - it depends on where you collect it and when.
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  12. Sean81

    Sean81 Member

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    I have a cheap one and when I calibrate off RO it is always way off. Never accurate at all. They are designed to work off the range they show and RO is to far off the scale. But if you have nothing then RO is great. Plus I might have a crap meter.

    Adam the 10 minutes to do the diy calibrating fluid is worth it. Put in sealed bottle and test from time to time.
  13. IJG3145

    IJG3145 Member

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    If you ask at your LFS you'll find calibrating fluid is in fact filtered sea water. NEVER use RO or you'll be ballpark at best. @Sean81 is spot on, they need to be calibrated to the range you are using it for.

    Calibration was discussed recently HERE.

    Basically any clean sea water will get you closer to accurate than non sea water. Remember that in your display stability is far more important than pinpoint accuracy.
    Last edited: Aug 25, 2016
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  14. Adam_w

    Adam_w Member

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    So my 2 best options would be - Collaroy Beach for some sea water.. I've filled up my tank with NSW from there before back when i was starting up and had no problems. I did read on a forum that a few reefers fill up at this beach so I didn't go in completely blind.

    There's a Jay car down the road too so if they have calibration fluid i could give that a go when the refractometre gets here

    With the sea water would hte bottle keep or should I go get fresh water every time i wanted to test?

    Thanks again :)
  15. IJG3145

    IJG3145 Member

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    If you keep the lid off to an absolute minimum to stop evaporation, sea water and cal fluid will last years.
  16. macca_75

    macca_75 Member

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    @Adam_w - if you use this seawater you are collecting for calibration, what number exactly are you going to set it to?

    If you don';t care about the number and only want to set it to be "the same as my local beach" then thats OK. If you care about knowing the number - this will ever work.

    For what it's worth the absolute number isn't really important - what is important is long term stability. That said wouldn't it be nice to know the number AND be able to track/monitor/measure stability?
  17. IJG3145

    IJG3145 Member

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    I agree, it's great to know then number. But given that PH is a result of other parameters anyway, it's those parameters that you need to get right. In the end you can't successfully alter PH directly anyway.
  18. Adam_w

    Adam_w Member

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    So I've checked with a refractometer that measures in Brix? I think my brother bought it to use it with his beer brewing haha

    Anyway salt is all good! I think i might need to sort an ATO i fill up a little bit every few days as it is so its ok for the moment.

    Thinking of adding another light too though because its a 3 foot tank with just an AI prime over the middle section. I've got good health and growth there on my corals but the sides are a bit dark so they're empty.

    That will be the next project just reading up on the DIY lights on this forum now!

    Thanks for help everyone
  19. IJG3145

    IJG3145 Member

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    BRIX is for measuring sugar and unfortunately it is totally useless for marine. They have to be for specic purposes. From memory we had about 7 different ones when I did my trade, including brix which allowed us to check consitancy on sugar based glues.
  20. Adam_w

    Adam_w Member

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    Well then the more you know - on the article posted above about the refractometers there was a section for Brix? Anyway mine should be arriving some time this week, I have to assume mine is going okay for the moment.. new birdsnest and club coral seem to be doing okay

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