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#1
12/21/2007, 05:49 PM
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calibrate your refractometer!
I brought home a fish from the lfs and decided to test the salinity of the lfs water with my refractometer. It measured 1.033!! I couldn't believe it and was pretty irritated with the store for not properly monitoring their salinity.
I recently read some posts about calibrating refractometers using solutions with a salinity close to that of natural seawater. I had only calibrated mine with pure water. I made up Randy's calibration fluid that should be right around 1.026 and couldn't believe it when my refractometer read 1.033! I guess the lfs was right on! So, my reef, which I thought was running at 1.026 is actually 1.021. I'll have to slowly raise that. So, the question arises, should I invest in a new, maybe more accurate refractometer or now that mine is calibrated should it be ok to continue to use? It's a cheapo one from Ebay that I bought about 3 years ago. You know, this might also explain my recent bad luck with a couple of online fish orders in which I set my qt tank salinity to that of what the online vendor told me they shipped their fish in. 
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Every time they make something idiot proof, they build a better idiot. |
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#2
12/21/2007, 05:58 PM
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Oh, and I just tested the calibration solution with my old swing arm and it measured 1.025. Should have been using that all along...
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Every time they make something idiot proof, they build a better idiot. |
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#3
12/21/2007, 06:00 PM
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YEP I did the exact same thing. My refracto I got from PA was .08 too high. Randy's solution was right on at 1.026
Chris
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In search of the illusive pinky toenail. |
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#5
12/21/2007, 06:34 PM
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It seems a common theme that refractometers calibrated using purified water are a few thousandths off. I too bought the 53.0mS Calibration fluid and found that my refractometer has been off 3/1000ths for over a year (like you mine was giving a false high). I posted on here and someone suggested that once calibrated, on a monthly basis or so check it against the calibration fluid. No need to get another refractometer, it would most likely give you a false high anyway. Now that yours is calibrated correctly, it is a very accurate measure of specific gravity/salinity.
BTW, you might want to increase your specific gravity the way I did, which was to replace evaporated water with full strength salt water. That way you slowly, incrementally increase you sg over several days. Ironically, those cheap swing arm hydrometers were actually giving me more accurate readings than my refractometer before I calibrated correctly. lol |
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#6
12/21/2007, 07:08 PM
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Quote:
__________________
Every time they make something idiot proof, they build a better idiot. |
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#7
12/22/2007, 09:26 AM
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Can someone link me to randys refract calibration solution page? Mine says to use distilled water but i keep reading that it might be off with that method. My reef looks great but id still like to double check.
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#8
12/22/2007, 09:33 AM
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I found it, the search is working.
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#10
12/31/2007, 12:04 AM
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Refractometers and Salinity Measurement
http://reefkeeping.com/issues/2006-12/rhf/index.php Let me know if you have any questions. And if you are buying a 53mS calibration solution buy only the Pinpoint 53mS.
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If you See Me Running You Better Catch-Up An explosion can be defined as a loud noise, accompanied by the sudden going away of things, from a place where they use to be. |
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#11
12/31/2007, 12:18 AM
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Quote:
I just bought the pin point 53ms solution---what reading on the spectrometer should I be looking for when using it?
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"evrr bean to sea Billy--evrr smelled a fish?" "Aye capn..experience is the best teacher" |
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#12
12/31/2007, 12:47 AM
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http://reefkeeping.com/issues/2004-06/rhf/index.php
Thats the one i used. "This 3.65 weight percent sodium chloride solution can be made by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified freshwater." |
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#13
12/31/2007, 02:30 AM
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capn, what do you mean spectrophotmeter ? There is no such thing for salinity. Or did you mean Refractometer ? If that, you put a drop on the slip and turn the cal screw until it reads 35 ppt or 1.0264 SG
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If you See Me Running You Better Catch-Up An explosion can be defined as a loud noise, accompanied by the sudden going away of things, from a place where they use to be. |
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#14
12/31/2007, 05:34 AM
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Boomer, I made up the calibration solution yesterday using 1/4 cup salt plus one teaspoon salt mixed in 2L of RO/DI water. The salt would not completely dissolve in the water after at least a half hour of stirring, setting, etc. Should the water be perfectly clear and should the salt be completely dissolved or should there be a small amount of salt that does not completely dissolve? When I tested some of the solution it was within a hundredth or so of 1.026 or 35ppt. Any insight? Thanks.
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Freed |
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#15
12/31/2007, 10:43 AM
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FWIW After I went to the effort of making Randys calibration solution for the refractometer I took the refracto to the Florida Aquarium (I used to live within walking distance) and had them verify my refractometer was accurate. It was right on the money!
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In search of the illusive pinky toenail. |
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#16
12/31/2007, 10:48 AM
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FWIW After I went to the effort of making Randys calibration solution for the refractometer I took the refracto to the Florida Aquarium (I used to live within walking distance) and had them verify my refractometer was accurate. It was right on the money!
It was right on after calibration to the DIY solution, or without that step?
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Randy Holmes-Farley |
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#17
12/31/2007, 10:51 AM
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Hi Randy! It was right on after calibration with the DIY solution. After I calibrated it I took it over to the Florida Aquarium.
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In search of the illusive pinky toenail. |
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#18
12/31/2007, 11:36 AM
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Freed
When you say salt do you mean seasalt mix or Morton table salt ? It is Morton table salt you use not no seasalt mix.
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If you See Me Running You Better Catch-Up An explosion can be defined as a loud noise, accompanied by the sudden going away of things, from a place where they use to be. |
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#19
12/31/2007, 01:40 PM
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Quote:
__________________
"evrr bean to sea Billy--evrr smelled a fish?" "Aye capn..experience is the best teacher" |
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#20
12/31/2007, 01:54 PM
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Great. I'm glad the DIY worked well for you.
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Randy Holmes-Farley |
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#21
12/31/2007, 02:17 PM
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__________________
In search of the illusive pinky toenail. |
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#22
12/31/2007, 03:11 PM
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Quote:
When I tested it on the refracometer I got 1.030. Would you guys recommend that I assume this is fairly accurate or should I wait till I can get some of the pinpoint solution? Thanks, Steve |
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#23
12/31/2007, 03:22 PM
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How much didn't dissolve? If a tiny bit compared to what you added, just ignore it.
To answer the what to do question, how did you measure volumes?
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Randy Holmes-Farley |
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#24
12/31/2007, 03:32 PM
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Quote:
Yes, just a tiny bit didn't dissolve. I measured out the RO/DI water with a two liter bottle filled all the way to the top and I used 1/4 cup + 1 teaspoon of Mortons Iodized salt. I over filled both of them and leveled them off with a straight edge. I then poured the water into a clean bucket and slowly added the salt while I was stirring the water. Steve Last edited by shoops; 12/31/2007 at 03:42 PM. |
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#25
12/31/2007, 03:33 PM
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Another question when using the 2L bottles, when filling, is that all the way to the lip so that it overflows? Or a little less such as when you get a new bottle of soda it is not filled to the top?
Thanks. |
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