Salinity Calibration Solution Problems

[crimper]

I had the same issue 3 months ago. All the while I was using distilled water to calibrate my refractometer until I bought some corals from a fellow reefer and told me his parameters (salinity: 35ppt). As always, I test the salinity of the water that the new frag came from and noticed it was 40ppt. His parameters cant be off, as this guy is running one of the most successful SPS tank that I've seen since I started this hobby.

I then immediately bought a pinpoint calibration fluid and re-calibrated my refractometer to check.

To my surprise... all my tanks were 5ppt off. From then on I re-calibrate my refractometer with the Pinpoint Calibration fluid almost every time I'm using it.