Tank Journal Archive

newTOreef

Member
Nov 16, 2013
60
28
Refractometer Calibration Test
ok, so my refractometer came in today, i had heard alot of people state using ro water was the way to calibrate then another set of people argue that calibration fluid was the go, so thought i would test, first i zeroed the refractometer using rodi water, then took a reading of my tank water to which i got a result of 1.023, i them wiped the lense clean zeroed again, then calibrated it to 1.023 using 1.023 calibration solution supplied by majestic aquariums, then again wiped the lense clean and tested my tank water to whock i got a reading of 1.026, which is what i had been mixing my salt quantities to except omly ever had a cheap swing arm that was never accurate anyway so always relied on my lfs to check when id go in, to make sure my refractometer wasnt out, i went to my lfs and fot them to check with theres and i got again 1.026, i asked what they calibrated theres with and there answer was 1.023 calibration solution, so the outcome of the test was mine was out 3 degrees by zeroing it with ro water comapired to using the solution
 

DavidS

The Resident Loony
Jul 17, 2011
3,337
1,033
Ballarat, Victoria
Interesting (yet not terribly surprising) results.... it's nice to see people actually taking the time to apply some scientific thinking to it!

As a curiosity point, did you verify that your RO/DI had a TDS of 0 before you did your initial calibration? And what does your refractometer tell you the SG of the RO/DI water is now that you've calibrated at 1.023?

The conclusion that can be drawn here based on what you have determined though is the same as the conjecture that already exists: for some people using RO/DI as a calibration is entirely accurate (and there will be plenty of people who've gone to the same lengths to determine that), and for others it's completely out of whack (hence were totally justified in using calibration fluid).
There could be any combination of the water, refractometer, visual acuity of the tester, and which way they hold their tongues that determines which is most effective o_0
As with most things in this hobby - the correct way is the way that works for your particular situation ... Just don't be surprised when it doesn't work for someone else, and they pick holes in what you believe is "proof". Too many bloody variables in this hobby for anything to be that simple :P
 

newTOreef

Member
Nov 16, 2013
60
28
hey david, good words, couldnt agree more, i didn't actually do a reverse test n see what my rodi was after calibrating with 1.023, but thats a good idea and i will do that tomorrow, to answer your question, yes i did test the rodi water using my tds meter prior to calibration and it was reading 0.00ppm,