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Jkraft136
07/04/2010, 07:56 PM
So i picked up a new refractometer today after my old one wouldn't hold calibration. So to test it out i check my tank. Too my shock it was reading 1.030. Got out my calibration fluid and it was reading 1.031. Then decided to do the ro water calibration and it was exactly at 0ppt. Now which do i trust the calibration fluid thats a few months old or the ro reading?

Percula9
07/04/2010, 08:10 PM
Take the calibration fluid and set your refractometer to read 35ppt. Then measure your tank water.

Jkraft136
07/04/2010, 08:27 PM
If i calibrate with the fluid the tank reads 1.026. The reason im skeptical about this is because the solution is about 6 months old and almost gone. Also there have been times that i've forgotten to screw back on the lid for hours at a time.

reef_doug
07/04/2010, 08:33 PM
Is it the Pinpoint brand 53mS fluid?

If so then calibrate the refract to the fluid at 35ppt and not RO/DI. Since the lid was off for only a couple hours it may not be off by much, but new fluid is only like $5 I think.

Percula9
07/04/2010, 08:35 PM
Get new calibration fluid.

Jkraft136
07/04/2010, 09:17 PM
Well im about to make my own calibration fluid. Will any iodized table salt work? Also do you fill up the 2liter bottle to the top then add salt, add salt then fill up the bottle to the top, or fill up with water dump into a bowl then mix the salt?

iamwrasseman
07/04/2010, 09:31 PM
as stated by Percula9 "get new calibration fluid" as that will solve all your problems and also be accurate .
i do have a question though about your statement above that your fluid is six months old and almost gone ,where did it go ?
have you re calibrated that many times in the last six months ?
if so why ?
if your refractometer needs to be re calibrated that often then i also would suggest that you spend the money for a new refractometer .

Jkraft136
07/04/2010, 09:33 PM
I'm MAKING my own calibration fluid instead of buying it, I just purchased a new refractometer because my other one wouldn't hold the calibration after a few days.

iamwrasseman
07/04/2010, 09:37 PM
okay , i really cant help you but would just be a bit apprehensive on the accuracy of making your own fluid . hope it all works out well for you as I'm just trying to help .

TheH
07/04/2010, 10:17 PM
Randy Holmes Farley has a standard recipe for DIY calibration fluid somewhere around here...

reef_doug
07/04/2010, 11:03 PM
Randy Holmes Farley has a standard recipe for DIY calibration fluid somewhere around here...

It requires Morton Iodized salt from the grocery store;

Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm

I personally use the Pinpoint brand 53 mS calibration solution. The brand is important... this is known as the only commercially available solution that would work w/ refractometers to 35 ppt.

iamwrasseman
07/05/2010, 12:34 PM
with a 1ppt error ?
2 litre bottles that dont measure 2 litre and are different size ?
VS
calibration fluid

hmmmmmm lets see i save $8 on my $10,000 ? ie. not a good trade off if you ask me.