Salinity meters/hydrometers

[NAS]

I have a refractometer. I use it to calibrate my Sea Test Hydrometer. I have found that my hydrometer is out by .03! So, when I use it on a day to day basis i just add .03 to it and it's corrected. The real key is having the consistient salinity. That includes same salinity in the tank and water change salinity.

I re-test my hydrometer every time I do a water change just to make sure it holds.