DON'T forget to do this like I have!

[SnowManSnow]

So, I've been noticing some unexplained issues with my tank over the last few months. Water is good... temp fine.. everything in check. Nothing dying off really, but things just weren't looking as good as they should given the parameters I keep my tank at.

Today I checked the calibration of my refractometer. While it wasn't WAAAAY of, it was off enough to stunt the growth of a lot of things and concern the fish. I've been running my tank at 30ppt (I thought it was 35)!

So, don't forget to check the calibration of your refractometer!!!!!

ATM I'm cooling my house down a few degrees to 68 so I can get the needed ambient temp to set it correctly haha.

B

 

[iseeweed]

So how do you calibrate?? I have heard of a table salt method?

 

[SnowManSnow]

what? table salt haha? table salt scares me a little No.. I just use distilled water and calibrate SG and PPT to 0 with the calibration screw.

 

[Anonymous]

with pure water you still might be off.
http://reefkeeping.com/issues/2006-12/rhf/index.php
Search for the word slope in the following article.

IMO making a solution that you can compare against is your best bet, or hell if anything buy it online.

 

[SnowManSnow]

what about using water out of my RODI machine with 0TDS output? would that be ok to calibrate too?

B

 

[Anonymous]

what about using water out of my RODI machine with 0TDS output? would that be ok to calibrate too?

B

It will calibrate it at 0 ppt, but you're interested in calibrating it at or near 35 ppt.

In the link sfsu provided Randy talks about how to obtain a 35ppt standard for refractometers.

 

[Anonymous]

what about using water out of my RODI machine with 0TDS output? would that be ok to calibrate too?

B

Refrac can't tell the difference between tap water and RODI, so just use tap water for the zero calibration.

I agree with Randy that you should calibrate the instrument across the range that you are going to use, FWIW.

 

[trido]

Try some pinpoint marine calibration solution Snowman. I used to calibrate mine at zero too (It was still a few points off) but once a friend taught me about slope and let me borrow some solution I haven turned back.

On another note, I just went through the exact same thing last week.