what are the effects of high salinity on sps?

[MitchM]

Actually, measuring salt water mixes by weight is the more accurate, measuring by specific gravity is less so, because for sg readings it depends on what temperature the water is.
I understand now how your refractometer could have messed things up.
Your refractometer should say in it's viewing window what temperature it was calibrated to at the factory.
Can I ask what calibration fluid you used, also which article you read regarding the difference between distilled and R/O?