Ya man, hanna confirms it on a thread here on r2r. If you find hannas pfficial thread and read through they explain it. The tester uses conductivity. A refractometer uses refraction of light. The conductivity solution does not work on a refractometer...
Yeah found that while I was laying in bed. I was nervous I had screwed something up. I used my hanna to calibrate the refractor and then had a second solution that I tested and it was spot on now. I found that thread after it was posted that you can't use it for calibrating the refractormeter.
Thanks Guys will raise up the salinity over the next few days to 1.025, Guessing it was running around 1.023-1.022 which isn't horrible but would explain why my zoas don't want to open up all the time.
So the Hanna solution to calibrate the digachecker and zero the refractometer to clean pure water then try them both on your tank and see if numbers match up? If not I'd say your fractor is ffed